controllers: move controllers base class from lib/base to controllers TG quickstart put it in lib/base.py , but it fits better on the controllers layer as a base there. The contributing docs were a bit ahead of time ... but with a typo.

# requirements.txt file for use as "pip install -r requirements.txt" as a
# readthedocs compatible alternative to "pip install -e ." which is a working
# alternative to "setup.py develop" which doesn't work with Mercurial 3.7
.