Update config.py for packaging

 - Twython requires a callback_url
 - The auth code (PIN) must now be passed to Twitter
 - Fix error in Twython instantiation
 - Export data_dir and log_dir instead of just config_dir
 - Other minor changes
Create __init__.py for package
Proxy requests to other endpoints to the Twitter API

 - Adapted from https://github.com/drdrang/drtwoot/blob/master/twitter.cgi
 - For use with Dr Twoot
Update server.py (née twitter-timeline-cache.py) for packaging

 - Rename twitter-timeline-cache.py -> server.py
 - Make imports relative
 - Switch from the deprecated data_dir to log_dir