Travis no longer supports Python 2.5.

http://blog.travis-ci.com/2013-11-18-upcoming-build-environment-updates/
Merge pull request #21 from agriffis/travis-python-2.5

Travis no longer supports Python 2.5.
Fix a comment.
Allow QueryString.add_param() to work with int values.

This seems to happen to me all the time, where higher level code assigns
integer values and then we get a traceback.  Seems harmless to handle
integer querystring values.

This will allow me to avoid the following hack in my code:

    # HACK since URLObject doesn't like ints in query values.
    data = {k: str(v) if isinstance(v, int) else v
            for k, v in data.items()}
    url = url.set_query_params(**data)
Move integer check into qs_encode()