v0.7.1dev, separated query parsing, more tests

- Separated query parsing into a helper function
- Added validity assertion to JointTable.get_samples
- Noted that IPython notebook display of d3.js based graph visualization for Bayesian network is really hacky (and therefore does not work properly at the moment)
- Moved version from setup.py to module.__version__
- Expanded test cases to cover helpers, JointTable, and JointTable learning from complete data
- Added some test skeletons to be filled out later