Added/updated version information

Fix for https://github.com/mitsuhiko/flask-babel/issues/45 *'Wrong version in documentation?'*; adding a `__version__` string to `flask_babel\__init__.py` and updating the existing version strings in `docs/conf.py`

Also updated the package name to `flask_babel` (in Python file headers/documentation) instead of `flaskext.babel` and/or `flask.ext.babel` (in accordance with http://flask.pocoo.org/docs/extensiondev/#anatomy-of-an-extension)