docs: fix some typos in comments and strings

Couple of typos fixed:
- occuring -> occurring
- imlement -> implement
- idenitifer -> identifer
etc...

Closes #5943

modules/angular2/src/compiler/shadow_css.ts

@@ -52,7 +52,7 @@ import {
     }
 
   * encapsultion: Styles defined within ShadowDOM, apply only to
-  dom inside the ShadowDOM. Polymer uses one of two techniques to imlement
+  dom inside the ShadowDOM. Polymer uses one of two techniques to implement
   this feature.
 
   By default, rules are prefixed with the host element tag name

modules/angular2/src/compiler/template_parser.ts

@@ -51,8 +51,8 @@ import {splitAtColon} from './util';
 // Group 3 = "on-"
 // Group 4 = "bindon-"
 // Group 5 = the identifier after "bind-", "var-/#", or "on-"
-// Group 6 = idenitifer inside [()]
-// Group 7 = idenitifer inside []
+// Group 6 = identifer inside [()]
+// Group 7 = identifer inside []
 // Group 8 = identifier inside ()
 var BIND_NAME_REGEXP =
     /^(?:(?:(?:(bind-)|(var-|#)|(on-)|(bindon-))(.+))|\[\(([^\)]+)\)\]|\[([^\]]+)\]|\(([^\)]+)\))$/g;

modules/angular2/src/compiler/util.ts

@@ -73,7 +73,7 @@ export function codeGenToString(expr: string): string {
   if (IS_DART) {
     return `'\${${expr}}'`;
   } else {
-    // JS automatically convets to string...
+    // JS automatically converts to string...
     return expr;
   }
 }

modules/angular2/src/compiler/xhr_mock.ts

@@ -5,7 +5,7 @@ import {BaseException, WrappedException} from 'angular2/src/facade/exceptions';
 import {PromiseCompleter, PromiseWrapper, Promise} from 'angular2/src/facade/async';
 
 /**
- * A mock implemenation of {@link XHR} that allows outgoing requests to be mocked
+ * A mock implementation of {@link XHR} that allows outgoing requests to be mocked
  * and responded to within a single test, without going to the network.
  */
 export class MockXHR extends XHR {