Regress: Many small updates to the docs

This updates corrects many typos, misspellings, inaccuracies, and
ambiguities in the varios multinomial regression and cox hazards docs.

Squashed commit of the following:

commit 0d9cbaf0b4e9050de62ae3335e2ce83cb8a7b12a
Author: Mark Wellons <mwellons@gopivotal.com>
Date:   Wed Jul 3 17:12:14 2013 -0700

    minor code review changes

commit 1d60fbe5781aa00e5f0eaad8b05219bc10fc1373
Author: Mark Wellons <mwellons@gopivotal.com>
Date:   Wed Jul 3 16:30:13 2013 -0700

    Minor change

commit 805eca69a46660cc7cc925adbe80002071fd9a1a
Author: Mark Wellons <mwellons@gopivotal.com>
Date:   Wed Jul 3 16:29:07 2013 -0700

    Many minor edits