Allow guzzle 3.7

Because lot of other dependencies rely on guzzle 3.7, and so it's impossible to satisfy everybody.
Merge branch 'refs/heads/patch-1'
Updated dependencies
Update changelog for 0.2.8
Merge pull request #124 from romainneutron/patch-1

Update changelog for 0.2.8
Merge pull request #1 from cboden/master

update