BREAKING CHANGE:
This change moves the http module into angular2/, so its import
path is now angular2/http instead of http/http.
Many other modules have also been moved around inside of angular2,
but the public API paths have not changed as of this commit.
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.
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
