Add exception classes, replace Exception by TimeoutError
Add handling of connection errors
Add handling of AuthenticationError
Add handling of APIError, InvalidRequestError
Update 400, 403, 404 handling
Replace ValueError by InvalidRequestError
Add handling of InvalidRequestError in ``to_python`
Merge branch 'master' into better-exceptions

Conflicts:
	pyuploadcare/__init__.py
Add checking of width, height in  __getattr__, fix raising of APIError
Get rid of ``ModernTestCase``.
Add unittest2 to test on Travis py 2.6
Merge pull request #32 from uploadcare/better-exceptions

Better exceptions