bugfix - now filtering out observed nodes -D
Merge pull request #23 from dmcnamee/master

BUG: now filtering out observed nodes in _partial_optimize
Bumped version to 0.5.1.
ENH: Generate stats after loading a model.
ENH: Added concatenate function for models.
ENH: Call gen_stats after creating new model.
Resolved conflicts.
ENH: Option to pass numpy array to observed node.
WIP: Allow for observed determinstic nodes.
Merge branch 'develop' of github.com:hddm-devs/kabuki into develop