feat(http): add basic http service

This implementation only works in JavaScript, while the Observable transpilation
story gets worked out. Right now, the service just makes a simple request,
and returns an Observable of Response.

Additional functionality will be captured in separate issues.

Fixes #2028

modules/angular2/src/http/http.ts

@@ -0,0 +1,68 @@
+/// <reference path="../../typings/rx/rx.all.d.ts" />
+
+import {Injectable} from 'angular2/src/di/decorators';
+import {RequestOptions, Connection} from './interfaces';
+import {Request} from './static_request';
+import {Response} from './static_response';
+import {XHRBackend} from './backends/xhr_backend';
+import {BaseRequestOptions} from './base_request_options';
+import * as Rx from 'rx';
+
+/**
+ * A function to perform http requests over XMLHttpRequest.
+ *
+ * #Example
+ *
+ * ```
+ * @Component({
+ *   appInjector: [httpBindings]
+ * })
+ * @View({
+ *   directives: [NgFor],
+ *   template: `
+ *     <ul>
+ *       <li *ng-for="#person of people">
+ *         hello, {{person.name}}
+ *       </li>
+ *     </ul>
+ *   `
+ * })
+ * class MyComponent {
+ *  constructor(http:Http) {
+ *    http('people.json').subscribe(res => this.people = res.json());
+ *  }
+ * }
+ * ```
+ *
+ *
+ * This function is bound to a single underlying connection mechanism, such as XHR, which could be
+ * mocked with dependency injection by replacing the `Backend` binding. For other transports, like
+ * JSONP or Node, a separate http function would be created, such as httpJSONP.
+ *
+ * @exportedAs angular2/http
+ *
+ **/
+
+// Abstract
+@Injectable()
+export class Http {
+}
+
+var Observable;
+if (Rx.hasOwnProperty('default')) {
+  Observable = (<any>Rx).default.Rx.Observable;
+} else {
+  Observable = Rx.Observable;
+}
+export function HttpFactory(backend: XHRBackend, defaultOptions: BaseRequestOptions) {
+  return function(url: string, options?: RequestOptions) {
+    return <Rx.Observable<Response>>(Observable.create(observer => {
+      var connection: Connection = backend.createConnection(new Request(url, options));
+      var internalSubscription = connection.response.subscribe(observer);
+      return () => {
+        internalSubscription.dispose();
+        connection.dispose();
+      }
+    }))
+  }
+}