Update faraday repo url.
Target faraday HEAD and bump dependencies.
`env` is no longer just a Hash.
Disable middleware specs until faraday-middleware works nice with faraday 0.9
`register_middleware` compatibility between 0.8 and 0.9.
Ruby 1.8 *sigh*.
Setup travis to test against Faraday HEAD and 0.8.
0.8 + 0.9 compat.
Remove 1.8.7 and 1.9.2 to reduce the build matrix
Fix up alternative gemfiles.
Update Faraday sha1 to remove `symbolize_keys` usage.
:scissors:
Merge branch 'master' into faraday-0.9

Conflicts:
  .travis.yml
Merge pull request #9 from plataformatec/faraday-0.9

Faraday 0.9