Make license GPLv3+ to be compatible with Apache-2 of MathJax
slight doc improvement

This example confused someone at [Trac 13621](http://trac.sagemath.org/sage_trac/ticket/13621).
Merge pull request #166 from kcrisman/patch-3

slight doc improvement
upgrade MathJax to version 2.2
Do not stop worksheets on Sign Out
Set default timeout to 0 as documented and make it configurable
Merge pull request #171 from novoselt/no-default-timeouting

Set default timeout to 0 as documented and make it configurable
Merge pull request #170 from novoselt/do-not-stop-worksheets

Do not stop worksheets on Sign Out
Merge pull request #167 from jhpalmieri/mathjax2.2

upgrade MathJax to version 2.2
Merge pull request #162 from ppurka/license

Make license GPLv3+ to be compatible with Apache-2 of MathJax