Make Http Angular 2 compliant

[SamVerschueren]

All the HTTP methods should transform their responses to observables to make it Angular 2 compliant.

• Return observables f98bdce
• Transform response to ng2 response
• Add possibility to inject extra options (see RequestOptions)

[SamVerschueren]

This isn't the only thing that should be done to make it angular 2 compliant. The response that is returned by the service should be a ng2 response object as well with methods like toJson(), etc.

Some references:

https://github.com/angular/angular/blob/2.0.0-beta.15/modules/angular2/src/http/http.ts
https://github.com/angular/angular/blob/2.0.0-beta.15/modules/angular2/src/http/static_response.ts

And what's up with that ConnectionBackend stuff?

https://github.com/angular/angular/blob/2.0.0-beta.15/modules/angular2/src/http/base_request_options.ts