feat(http): add support for ArrayBuffer

Add the buffer option to store response in ArrayBuffer
Improve the interface to get back response independently of the buffer type

modules/@angular/http/src/http_utils.ts

@@ -38,4 +38,12 @@ export function getResponseURL(xhr: any): string {
   return;
 }
 
+export function stringToArrayBuffer(string: String): ArrayBuffer {
+  let view = new Uint16Array(string.length);
+  for (var i = 0, strLen = string.length; i < strLen; i++) {
+    view[i] = string.charCodeAt(i);
+  }
+  return view.buffer;
+}
+
 export {isJsObject} from '../src/facade/lang';