SQLAlchemy + URL dispatch wiki tutorial

This tutorial introduces an SQLAlchemy and URL dispatch-based Pyramid application to a developer familiar with Python. When finished, the developer will have created a basic wiki application with authentication and authorization.

For cut and paste purposes, the source code for all stages of this tutorial can be browsed on GitHub for a specific branch or version under docs/tutorials/wiki2/src, which corresponds to the same location if you have Pyramid sources.