Switch to Guzzle 3.7+
Added Travis CI tests for PHP 5.5
Merge remote-tracking branch 'Mordred/master'

* Mordred/master:
  Switch to Guzzle 3.7+
Bumped version and added author
fix AccessToken refresh() bug

How did this pass the tests?
Bumped version
Password check should be wrapped with isset
Merge pull request #9 from tappleby/master

fix Client password() bug
Fix issue when authenticating with Google.

Google's HTTP reply to the authentication call included the charset in the Content-Type header ("appplication/json; charset=utf8" instead of simply "application/json"), so the simple string comparison was failing and the Response::parse() method was returning null and causing an exception in Keeguon/Multipass.
Bumped version
Updated to Guzzle 4 and fixed issues related to the update
Changed requirements regarding PHP now only >= 5.4
Refactored some code to make the library work w/ the new Guzzle API and updated tests.
Bumped version
Removed the 'clientOptions()' method from strategies since we now log in through the HTTP Authorization header and bumped version.
Added a way to switch the client authentication method when request tokens since not every provider supports the Authorization Header scheme and bumped version
Fixed parse mode handling for access token requests since it was throwing an Exception in Guzzle 4 and bumped version.
If the token method is POST params are now passed in the request body, added a body client auth scheme since some provider requires it and bumped version.
Fixed a fatal error introduced in the last version and bumped version.
Merge latest updates from upstream.