add test in gulpfile which will compile a basic TS file with generated
angular2.d.ts to ensure generated d.ts is valid syntactic TS
Adds support for enums in .d.ts generation pipeline.
Removes renaming reexports in http module.
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
