DOC: Add commit message style to dev guide
DOC: API doc output to _build/api_doc

...rather than at the same depth as the directory _build.  The goal is to
have all generated documentation under _build/.
change state representation from int to str in discretize

- discretize creates string states 's0', 's1', ... in its ofts field
- discretize explicitly passes adj - state map using a list, when adding transitions to ofts using add_adj
- sys.transitions.add_dj signature now requires state map as list
fixed save cmd + small formatting changes
new MealyMachine.simulate arg: current_state, demo in robot_gr1
bugfix: MealyMachine.simulate checked selected state with if not state to stop simulation, which fails when selecting state 0. Replaced by is None.
change LabeledTransitions.add_labeled_adj

new argument adj2states defining correspondence between adjacency matrix nodes and existing system states
update transys examples to use changed add_labeled_adj
fix robot_controlled_switching to work
updated examples to use modified add_labeled_adj
make the spec syntax in robot_continuous_pwa.py consistent with robot_continuous.py
change MathSet __repr__ to MathSet([...])
DOC: Collapsible sidebar, as seen on http://docs.python.org/
TRIV: Rename README so that GitHub parses as reST
minor restructuring of robot_continuous
more visualization in robot_continuous
shorten lines in prop2part, minor other changes
DOC: Epydoc no longer parses tulip/polytope/{esp,quickhull}.py
DOC: Initialize bibliography
DOC: Change to style like BibTeX alpha.bst

Also, I wrote instructions concerning this style and how to include
references in docstrings.