Update Guzzle Stereo to 1.2

Merge pull request #4 from estahn/update_1.2.0

Update to 1.2.0 and change composer type to symfony-bundle

Initial Release

Merge pull request #3 from estahn/downgrade_guzzle_stereo

Using guzzle-stero 1.1 since 1.2 is broken and has failing tests