patch: Save requests...HTTPSConnection

so that we unpatch back to the correct class in reset().

Closes #59
Merge pull request #63 from msabramo/issue_59_save_requests_HTTPSConnection

patch: Save requests...HTTPSConnection
Skip httplib2 tests if the lib can't be imported.
Tox environments for httplib2 testing.
Unpatch httplib2's SCHEME_TO_CONNECTION
Merge branch 'master' of https://github.com/kevin1024/vcrpy
Overwrite VCRConnectionMixin.connect() because httplib2 calls this
method and produce undesired connections in replay mode.