Added headers to the Digest.
Merge branch 'master' of https://github.com/soliantconsulting/stormpath-sdk-php into StormpathClient

Conflicts:
	src/Stormpath/Http/Client/Adapter/Digest.php
Added new test cases for the collections
Removed unwanted code
Removed the partition method
Merge pull request #6 from vinayganesh/StormpathClient

New Test cases added