Remove state leakage from resource instances
Use `include` to test strings

The components of the encoded data are in a different order
on different rubies
Isolate signature test
Only report build status based on master branch

[ci skip]
Merge pull request #13 from aceofsales/fix-travis-image

Only report build status based on master branch
Merge pull request #11 from aceofsales/fix-state-leakage

Remove state leakage from resource instances / Fix string tests
bumped version to 0.2.5
Added documentation for getting credentials through the new Chargify Direct settings page.

Fixes #14
fixes method chaining for call representation on request and response methods
bump version to 0.2.6