refactor(http): remove default settings from RequestOptions constructor

The BaseRequestOptions class is responsible for declaring default values,
while the RequestOptions class is merely responsible for setting values
based on values provided in the constructor.

modules/angular2/core.ts

@@ -17,5 +17,6 @@ export * from './src/core/compiler/dynamic_component_loader';
 export {ViewRef, ProtoViewRef} from './src/core/compiler/view_ref';
 export {ViewContainerRef} from './src/core/compiler/view_container_ref';
 export {ElementRef} from './src/core/compiler/element_ref';
+export {EventEmitter} from './src/facade/async';
 
 export {NgZone} from './src/core/zone/ng_zone';