Restructure OAuth2 tests.
PEP8 cleanup of test_signatures.
Fix scheme check for python 2.6.

urlparse.urlparse is buggy in python 2.6 and gives the netloc value to
scheme if no scheme is preset. Thus we check for both scheme and netloc.
Verification tests for all signature methods.
Merge branch 'master' of https://github.com/idan/oauthlib