feat: added support for realtime updates using snapshot listeners

It is now possible to listen to realtime update for documents and collection queries. Usage is
available in the README.

BREAKING CHANGE: Replaced @Google-Cloud dependency with firestore client SDK. Implementation of
realtime updates highlights discreptancies between the SDKS.

.gitignore

@@ -4,3 +4,4 @@ coverage
 .nyc_output
 service-account.json
 firebase-firestorm.code-workspace
+.env

README.md

@@ -9,6 +9,8 @@ Firestorm is an [ORM](https://en.wikipedia.org/wiki/Object-relational_mapping)
 for [firestore](https://firebase.google.com/docs/firestore) which can be used
 with Typescript.
 
+**This library currently only supports the [client Firebase SDK](https://github.com/firebase/firebase-js-sdk).**
+
 ## Contents
 
 -   [Requirements](#requirements)
@@ -134,7 +136,6 @@ import Comment from './Comment';
   name: 'posts',
 })
 export default class Post extends Entity {
-  ...
   @subCollection({
     name: 'comments',
     entity: Comment, // we must define the entity class due to limitations in Typescript's reflection capabilities. Progress should be made on this issue in future releases.
@@ -171,7 +172,6 @@ import Author from './Author';
   name: 'posts',
 })
 export default class Post extends Entity {
-  ...
   @documentRef({
     name: 'author',
     entity: Author, // we must define the entity class due to limitations in Typescript's reflection capabilities. Progress should be made on this issue in future releases.
@@ -190,11 +190,9 @@ use to manipulate the data.
 ##### Getting a document
 
 ```typescript
-...
 const post = Collection(Post).get('post-1').then((post : Post) => {
   console.log(post);
 });
-...
 ```
 
 ##### Getting a subcollection
@@ -215,56 +213,96 @@ const commentCollection = postRef.collection(Post);
 
 ##### Querying data
 
-You can use the `find(query : ICollectionQuery)` method to query data.
-A full list of options are available in the
-[docs](https://lmcq.github.io/firebase-firestorm/), but they are essentially
-the same as what is available with firestore.
+Calling `query()` on a collection will allow you to build queries in a [similar fashion to the standard Firestore SDK](https://firebase.google.com/docs/firestore/query-data/queries). You can build a query by chaining together methods, and finally calling the `get()` method to fetch the result. Omitting filters after the `query()` method will return all results from a collection.
 
 ```typescript
-  const posts = Collection(Post).find({
-    where: [
-      ['title', '==', 'Example Title'],
-      ...
-    ],
-  });
+// Build the query.
+const query = Collection(Post)
+  .query()
+  .where('title', '==', 'Example Title');
+
+// Fetch and manipulate the result.
+query.get().then((snapshot): DocumentSnapshot<Post> => {
+  const post = snapshot.doc;
+  ...
+});
 ```
 
 ##### Creating documents
 
 ```typescript
-...
-  const post = new Post();
-  post.id = 'post-1'; // id is optional, if it is not defined it will be generated by firestore.
-  post.title = 'Untitled';
-  let savedPost : Post;
-  Collection(Post).create(post).then((_savedPost : Post) => {
-    savedPost = _savedPost;
-  });
-...
+const post = new Post();
+post.id = 'post-1'; // id is optional, if it is not defined it will be generated by firestore.
+post.title = 'Untitled';
+let savedPost : Post;
+Collection(Post).create(post).then((_savedPost : Post) => {
+  savedPost = _savedPost;
+});
 ```
 
 ##### Updating documents
 
 ```typescript
-...
-  const post = new Post();
-  post.id = 'post-1'; // id is required.
-  post.title = 'Untitled';
-  let savedPost : Post;
-  Collection(Post).update(post).then((_savedPost : Post) => {
-    savedPost = _savedPost;
-  });
-...
+const post = new Post();
+post.id = 'post-1'; // id is required.
+post.title = 'Untitled';
+let savedPost : Post;
+Collection(Post).update(post).then((_savedPost: Post) => {
+  savedPost = _savedPost;
+});
 ```
 
 ##### Removing documents
 
 ```typescript
-...
-  Collection(Post).remove('post-id').then(...);
-...
+Collection(Post).remove('post-id').then(...);
 ```
 
+#### 5. Realtime Updates
+
+You can set up listeners for changes on either a single document, or a group of documents for a query. This is done a [similar way to the standard Firebase SDK](https://firebase.google.com/docs/firestore/query-data/listen).
+
+##### Listening to document updates
+
+You can attach a listener to a single document reference by using the `onSnapshot(callback)` method.
+
+````typescript
+Collection(Post).doc('post-id').onSnapshot(
+  (snapshot): DocumentSnapshot<Post> => {
+    const post: Post = snapshot.doc;
+  }
+);
+...
+````
+
+The callback function will executed once with the initial snapshot payload, and then for any subsequent updates to that document.
+
+##### Listening to a collection (or query)
+
+You can attach a listener to a group of documents in a collection by using the `onSnapshot(callback)` method on a collection query.
+
+````typescript
+Collection(Post).query().onSnapshot(
+  (snapshot): QuerySnapshot<Post> => {
+    const posts: Post[] = snapshot.docs;
+  }
+);
+
+// or
+
+Collection(Post)
+  .query()
+  .where('title', '==', 'Example Title')
+  .onSnapshot(
+    (snapshot): QuerySnapshot<Post> => {
+      const posts: Post[] = snapshot.docs;
+    }
+  );
+````
+The callback function will executed once with the initial snapshot payload, and then for any subsequent updates to that query. As per the Firebase SDK, you call see the [document changes in each snapshot](https://firebase.google.com/docs/firestore/query-data/listen#view_changes_between_snapshots) using the `snapshot.docChanges()` method.
+
+
+
 #### 6. Formatting data
 
 An instance of entity maybe contain properties such as
@@ -347,12 +385,10 @@ class Nested {
 And then to use this entity:
 
 ```typescript
-...
 const nested = new Nested();
 nested.nestedProperty = 'test';
 const example = new Example();
 example.nestedObject = nested;
-...
 ```
 
 #### Geopoints
@@ -372,10 +408,8 @@ class Example extends Entity {
 And then to assign a GeoPoint:
 
 ```typescript
-...
-  const example = new Example();
-  example.geopoint = new Geopoint(latitude, longitude);
-...
+const example = new Example();
+example.geopoint = new Geopoint(latitude, longitude);
 ```
 
 #### Timestamps
@@ -417,9 +451,7 @@ reference's have the `I` infront of the type, e.g. `IDocumentRef`,
 
 ## Limitations
 
--   Listening to document updates using snapshots is currently unsupported.
 -   Transactions and batched writes are currently unsupported.
--   Offline persitences is unsupported.
 
 If you would like to help resolve these issues, feel free
 to make a a [pull request](#pull-requests).

docs/classes/caseconverter.html

@@ -106,7 +106,7 @@ <h3><span class="tsd-flag ts-flagStatic">Static</span> camel<wbr>ToKebab<wbr>Cas
 						<li class="tsd-description">
 							<aside class="tsd-sources">
 								<ul>
-									<li>Defined in utils/CaseConverter.ts:25</li>
+									<li>Defined in <a href="https://github.com/lmcq/firebase-firestorm/blob/dba4fb3/src/utils/CaseConverter.ts#L25">utils/CaseConverter.ts:25</a></li>
 								</ul>
 							</aside>
 							<div class="tsd-comment tsd-typography">
@@ -140,7 +140,7 @@ <h3><span class="tsd-flag ts-flagStatic">Static</span> camel<wbr>ToSnake<wbr>Cas
 						<li class="tsd-description">
 							<aside class="tsd-sources">
 								<ul>
-									<li>Defined in utils/CaseConverter.ts:11</li>
+									<li>Defined in <a href="https://github.com/lmcq/firebase-firestorm/blob/dba4fb3/src/utils/CaseConverter.ts#L11">utils/CaseConverter.ts:11</a></li>
 								</ul>
 							</aside>
 							<div class="tsd-comment tsd-typography">
@@ -174,7 +174,7 @@ <h3><span class="tsd-flag ts-flagStatic">Static</span> to<wbr>Camel<wbr>Case</h3
 						<li class="tsd-description">
 							<aside class="tsd-sources">
 								<ul>
-									<li>Defined in utils/CaseConverter.ts:39</li>
+									<li>Defined in <a href="https://github.com/lmcq/firebase-firestorm/blob/dba4fb3/src/utils/CaseConverter.ts#L39">utils/CaseConverter.ts:39</a></li>
 								</ul>
 							</aside>
 							<div class="tsd-comment tsd-typography">