Replace http-streams with wreq. Details follow.

http-streams isn't very nice for several reasons:

* SSL is handled using an external dependency
* HsOpenSSL has issues with reentrancy
* No support for mulipart POST
* No support for session handling

wreq handles all of the points above and looks
quite nice based on a few hours of work. Since all
data manipulation is done using lens, the API has a
very uniform feeling. It does however imply a lens
dependency.
Bump zip-archive dependency.
Cleanup imports.
Force tight lower bound on aeson due to lens #450.
Bump version.