Include module name in log messages

Previously:

        [24666] 2014-07-02 15:35:45,996 INFO   Executing: spluigi
        [24666] 2014-07-02 15:35:46,195 INFO   /home/arash/spotify/repos/luigis/spotify_luigi/spotify/__init__.py:3: UserWarning: Module spotify was already imported from /home/arash/spotify/repos/luigis/spotify_luigi/spotify/__init__.py, but /usr/lib/python2.6/dist-packages is being added to sys.path

Now:

        [31349] 2014-07-02 15:47:50,598 INFO:root Executing: spluigi
        [31349] 2014-07-02 15:47:50,797 INFO:subprocess.spluigi /home/arash/spotify/repos/luigis/spotify_luigi/spotify/__init__.py:3: UserWarning: Module spotify was already imported from /home/arash/spotify/repos/luigis/spotify_luigi/spotify/__init__.py, but /usr/lib/python2.6/dist-packages is being added to sys.path
Log before running a command with logging
Always use run_with_logging

This ensures that we also log to the file logger
Log less to files, skip date and milliseconds
Shorten logger name for run_with_logging
Merge pull request #11 from Tarrasch/improve-logging

Improve logging