Create a custom exception hierarchy for exceptions that occur in the SDK.  A CanvasAPIError maps to HTTPErrors that might occur on the Canvas side.  These errors will contain the status code, json, and error message (string representation of the json).  Instead of catching HTTPErrors and re-raising them, CanvasAPIErrors will be raised instead.  Added some new tests.  Minor version bump.  Minor cleanup of retry logic.
Add .sublime-project settings file to project per Sublime doc recommendations.  Ignore the .sublime-workspace file that might be there as a result of using a project.  Add __unicode__ method to CanvasAPIError class definition and add tests for this class.
Add note about multiple formats of error json that Canvas can send back.  Update to project file due to removal of python_interpreter key.
Merge branch 'develop' into feature/sdk_custom_exception

Conflicts:
	.gitignore
Merge pull request #22 from penzance/feature/sdk_custom_exception

TLT-423 - Feature/sdk custom exception