Smooth over default settings for consistency

With the goal in mind of having a template that generates a project that
comes ready to be "runserver'd",  this commit makes a few changes to
settings and requirements to fix issues with raven, pyscopg2, and pyscss

- Use a stable version of pyscss in requirements.txt
- Remove raven middleware from default installed middleware
- Remove pyscopg2 from requirements since sqlite is the default database
  engine