[betaseries_list] add a plugin for querying the series from www.betaseries.com

Api key can be requested at http://www.betaseries.com/api.
The plugin is meant to work with the import_series plugin as follow:

        import_series:
          from:
            betaseries_list:
              username: xxxxx
              password: xxxxx
              api_key: xxxxx
[betaseries_list] remove the ability to define 'members' as null in the config
[betaseries_list] anticipate Python 3 compatibility
[betaseries_list] Sphinx compliant docstrings
[betaseries_list] fix examples
[betaseries_list] fix tests

importing the flexget.plugins.filter.series in this module was making lots of other tests to fail
Merge remote-tracking branch 'flexget/master' into plugin_betaseries_list
[betaseries_list] fix tests (better)
Merge pull request #101 from thomasleveil/plugin_betaseries_list

[betaseries_list] add a plugin for querying the series from www.betaseri...