update python distribute

Hi all,

the latest svn snapshot of obspy.core needs a more recent distribute
version. In case you have problems during an update go to..

..and follow the installation instructions from source.
If you are working with a virtual Python environment be sure to specify
your local path like..

$ python setup.py install --prefix=/home/me/local

..or whatever place your local environment is in.

best,
Tobias