replace Slot with VarTree for VariableTrees, doc fixes fomr Keith
implement tests
start updating docs
Merge branch 'master' of github.com:swryan/nreltraining2013

FIXED Conflicts:
	docs/conf.py
	docs/srcdocs.rst
update docs
a couple of tweaks to docs
edit
Merge branch 'master' of github.com:swryan/nreltraining2013
fixed fd nonsense, addressed #3
Merge pull request #1 from JustinSGray/master

fixed fd nonsense, addressed #3
Merge pull request #2 from swryan/master

add test cases and update docs