bin/gmg command adduser generates a minor unnecessary error

[NattilyPidgin]

Whenever bin/gmg adduser is used, a minor error is raised because the code filters the User table for a unicode string using a non-unicode string. This is the error that is raised:

mediagoblin/local/lib/python2.7/site-packages/SQLAlchemy-0.8.2-py2.7-linux-i686.egg/sqlalchemy/engine/default.py:459: SAWarning: Unicode type received non-unicode bind param value.
  param.append(processors[key](compiled_params[key]))

This doesn't affect functionality at all, but may be confusing if unfixed.

[NattilyPidgin]

And here is my commit with a 2 line fix to this error :P
​https://gitorious.org/mediagoblin/npigeons-mediagoblin/source/3f09af3de33c8c670923edc122d1e6a86281b2a2:

[Christopher Allan Webber]

Merged, rebased, and pushed.

[Christopher Allan Webber]

Thanks npigeon!