Made it possible for GatewayQuizzes to have either an infinite number of attempts, or an infinite amount of time per test (or both)
Fixed bug with unitialized varaibel
The my mathjax link was hardcoded and not relative.  I changed it to the 2.8 version.

Merge branch 'release/2.8' of http://github.com/openwebwork/webwork2 into gatewayups

Conflicts:
	htdocs/mathjax
Merge pull request #204 from goehle/gatewayups

Gateway Upgrades