Take tornado out of install_requires
add deps for doc server
Make renderer modules actually work. Pull in aspen-tornado if you run the docs server.
Fix renderer_default config setting via conf file
Reorganized configuration/__init__.py a little
Switched 'make docs' back to specifying the default renderer in the
  config file
Fix string formatting to be 2.6 compatible
fix travis badge to point at the current travis runs
Release 0.25.0
Bump version to 0.25.0-dev
Heroku needs aspen-tornado
add a changelog
Fix issue #172 - better error
Merge branch 'master' into issue159

Conflicts:
	setup.py