Update readme to accurately reflect what was decided on issue #10

See comments here:
#10 (comment)

readme.md

@@ -39,6 +39,23 @@ Then use the method search to perform a search
     var result = searcher.search(query)
 ```
 
+Updating the index
+------------------
+
+After you create your `searcher`, you can add documents to it using `searcher.add()`.
+
+```javascript
+    var data = ["survey","surgery","insurgence"];
+    var searcher = new FuzzySearch({source:data});
+    var query = "assurance";
+    var result = searcher.search(query)
+    var newEntry = "surgeon";
+    searcher.add(newEntry);
+    var newResult = searcher.search("surgeo");
+```
+
+The API also supports more advanced tag-based search. See the `Tagged search` section below.
+
 Twitter typeahead
 ----------------
 
@@ -657,20 +674,6 @@ Comparison of some string similarity measurements
 > https://asecuritysite.com/forensics/simstring
 
 
-Internal Design
-===============
-
-Internally, there are 2 main datastructures that are maintained, `this.source` and `this.index`:
-* `this.source` - the original source data
-* `this.index` - the indexed data for use in searching
-
-The method `this._prepSource` inspects `this.source` and builds `this.index`. `this._prepSource` add each item in source to `this.index` by calling `this.add()`. `this.add()` in turn calls `this._prepItem()` before adding the item to the index.
-
-If the `this.dirty` flag is set to `true`, reindexing will happen upon the next search.
-
-A good summary of how indexing works and how the code is organized can be found in [this issue comment from @jeancroy](https://github.com/jeancroy/FuzzySearch/issues/9#issuecomment-349845521)
-
-
 Tests
 =====