Update snapshot fetch documentation

README.md

@@ -256,7 +256,7 @@ Get a read-only snapshot of a document at the requested version.
 * `id` _(String)_
   ID of the snapshot
 * `version` _(number) [optional]_
-  The version number of the desired snapshot
+  The version number of the desired snapshot. If `null`, the latest version is fetched.
 * `callback` _(Function)_
   Called with `(error, snapshot)`, where `snapshot` takes the following form:
 
@@ -277,7 +277,7 @@ Get a read-only snapshot of a document at the requested version.
 * `id` _(String)_
   ID of the snapshot
 * `timestamp` _(number) [optional]_
-  The timestamp of the desired snapshot. The returned snapshot will be the latest snapshot before the provided timestamp
+  The timestamp of the desired snapshot. The returned snapshot will be the latest snapshot before the provided timestamp. If `null`, the latest version is fetched.
 * `callback` _(Function)_
   Called with `(error, snapshot)`, where `snapshot` takes the following form:
 

lib/client/connection.js

@@ -618,7 +618,7 @@ Connection.prototype._firstSnapshotRequest = function () {
  *
  * @param collection - the collection name of the snapshot
  * @param id - the ID of the snapshot
- * @param version (optional) - the version number to fetch
+ * @param version (optional) - the version number to fetch. If null, the latest version is fetched.
  * @param callback - (error, snapshot) => void, where snapshot takes the following schema:
  *
  * {
@@ -646,7 +646,7 @@ Connection.prototype.fetchSnapshot = function(collection, id, version, callback)
  *
  * @param collection - the collection name of the snapshot
  * @param id - the ID of the snapshot
- * @param timestamp (optional) - the timestamp to fetch
+ * @param timestamp (optional) - the timestamp to fetch. If null, the latest version is fetched.
  * @param callback - (error, snapshot) => void, where snapshot takes the following schema:
  *
  * {