String to Authority conversion bugfix

The "authority" call on GrantedAuthority seems to have a logic error. I've attached a patch and unit test.

I've also added an additional test called "testSubstringAuthority" which is ignored. I wasn't sure what the desired behavior should be if an authority contain the phrase "uaa.admin". For example, "truluaa.adminbob" shouldn't give you "uaa.admin", but I'm not sure if it was coded that way for a reason.