Bbai

* Add DeltaBinomialModel to model the difference of two binomial distribution probabilities

* Hypothesis testing for mean of normally distributed data with unknown variance using encompassing expected intrinsic Bayes factor (EEIBF)

* Add support for building adaptive sparse grids. (See example [13](https://github.com/rnburn/bbai/blob/master/example/13-sparse-grid.ipynb))

* Make numeric integration more accurate

Add BayessianGaussianProcessRegression model for doing Objective Bayesian analysis with reference priors.

* Support Fitting Logistic Regression Models with Jeffrey's Prior