Edited definitions of chbevl to fix #549
Tweak to .travis.yml to fix MPL display problem; fixed some math in the docs
Changed MathJax to use https server
Added utility function for calculating posterior predictive p-values
Renamed post_pred_check to ppp_value and moved it to the diagnostics module
Greatly simplified ppp_value
Added Slice sampler to 2.3 code base
Incremented version number to 2.3.3
Tweaked Slicer to support vector-valued stochastics
Fixes to slice sampler
Merge branch '2.3_slice' of github.com:pymc-devs/pymc into 2.3_slice