Make minor edits to Bayesian material

This commit makes a minor change to the Bayesian material (on the
priors), adds a reference and corrects a bibtex record call.
Reorder inference material

This commit moves the LRT discussion before hypothesis testing
in linear regression.
Rewrite intro to hypothesis testing

Like most of the recent changes, this one rewrites the introduction
to the inference material so that it uses sentences and paragraphs.
Rewrite overview of the Likelihood Ratio Test

This commit rewrites the treatment of the LRT, making it a bit more
natural.
Correct minor typo in linear regression material

The old version uses the wrong definition of R-square.
Edit material on constrained linear regression

This commit is a rewrite of the constrained linear regression
material so that it uses sentences, etc (the usual).