Port flask_fas_openid into Flask 0.10.0+

- Frozenset are not JSON serializable
- Don't use flask.session to store the openid information but rather a local dictionnary
pep8 fixes
Use a custom JSONEncoder to support frozenset and flask 0.10
Simply the isinstance check by checking for two types at once
Rework the version parsing according to @abadger's suggestions
Merge pull request #61 from fedora-infra/feature/flask010

Feature/flask010