Merge pull request #79 from paultpearson/master

Update linear algebra problems (Rochester=all and TCNJ=many) to MathObjects.

I thought I had seen it in the Files Changed link, but cannot find it now, so I guess I was mistaken.
New stat problem.
suject->subject
New probaility problem.
Fixups
Merge branch 'master' of github.com:openwebwork/webwork-open-problem-library
Fix OPL tags in linear algebra pg files from Rochester and TCNJ