upgrade to the latest requests and requests_oauthlib

`requests_oauthlib==0.3.3` does not work with the latest oauth>=0.7.0 anymore.

https://github.com/Chive/pyrate/pull/6 is a quickfix to use the older oauth. It would be cleaner to make `pyrate` support the latest versions of `requests` and `requests_oauthlib` instead though.
