Making guid field an md5 hash.

This is due to some issues with mysql indexes on text fields and
in order to simplify all over.
Adding BeautifulSoup as requirement to setup.py.
Bump version to 0.2.0!
Fixing version.
Moving setting USER_AGENT inside a our namespace settings var: PLANET.
Adding prefix 'planet_' to all comands.
Bumping version to 0.2.1.