Added Python3 support

Closes #36

* Running 2to3.py
* Oauth2 doesn't support Python 3, so replaced with requets-oauthlib (this also cleans up the multipart post magic)
* Cleaning up (using PyLint)

The majority of the edits are due to the PyLint fixes. I'll look at adding Pylint scoring to Travis-CI, to avoid the need for cleanups in the future.

@jmathai, @walkah: I'd appreciate any comments. I'll pull this to a "python3" branch, to make testing easier.