Added multilevel navigation.
Added a warning that the test code is also used in the docs.
Improved context variable names.

Replaced tabs_parent with parent_tabs and tabs_children with child_tabs.
Merge pull request #5 from inqbus-gmbh/multilevel

Added multilevel navigation.
Trivial doc fixes
Updated README, bumped version number
Added virtualenv support to sphinx makefile
Use blue theme for readthedocs too, version bump in docs
Improved docs
Added long_description to setup.py
Updated description in README