feat(__init__.py): Do not copy local repository

Not reall needed and speeds things up significantly.
feat(__init__.py): Do not delete local repository.

See previous commit to see why this is needed. d'oh.
feat(util.py): Do not clone entire history

Clone with a --depth=1 to only get most recent stuff.
feat(docfu.cli.py): Add logging option

-l or --log-file to specify where to log to
feat(cli,log): Logging actually happens

Saves logs in respective docs folder by default if no log file
is provided. Otherwise absolute path to the logfile given via command
line is used.
feat(__init__.py): Cleaner log formatting