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/enums.ts

@@ -0,0 +1,12 @@
+
+export enum RequestModesOpts { Cors, NoCors, SameOrigin };
+
+export enum RequestCacheOpts { Default, NoStore, Reload, NoCache, ForceCache, OnlyIfCached };
+
+export enum RequestCredentialsOpts { Omit, SameOrigin, Include };
+
+export enum RequestMethods { GET, POST, PUT, DELETE, OPTIONS, HEAD };
+
+export enum ReadyStates { UNSENT, OPEN, HEADERS_RECEIVED, LOADING, DONE, CANCELLED };
+
+export enum ResponseTypes { Basic, Cors, Default, Error, Opaque }