updates to project plugins:

 - force projects to return unicode names and branches, or None
 - refactor ProjectMap to set project name from cfg file
 - pass configs to find_project() as dict from plugin's cfg section
 - clean up git project class

updates to config file:

 - rename ~/.wakatime.conf to ~/.wakatime.cfg
 - better error handling while parsing and getting configs
 - no longer need to set defaults when parsing config file
 - use configparser for python3 when python2 import fails