Proposed documentation layout

Installation will describe the different options for installing Flask-Simon.

Quickstart will be a simple walkthrough of the using Flask-Simon.

Configuration will discuss what configuration settings are used by Flask-Simon

API will contain the autodoc output for `flask_simon.Simon`.

Further Reading will provide links to the documentation for Simon and MongoDB
Add get_or_404() to __all__

As part of the public API of Flask-Simon, `get_or_404()` needs to be included in `__all__`. Also, according to PEP8, `__all__` should appear after any imports.
Add docstrings
Add PyMongo as a requirement

Even though the Simon setup script will take care of this for us, it's a good idea to be explicit with all requirements.