added spec test for username validation

[larsks]

These spec tests run through several different usernames to test
the username validation code.

[larsks]

Note that I expect travis to fail this commit; according to ashp on irc, foo@ is valid, but this is currently rejected by the validate method.

[igalic]

@larsks is this in any way shape or form related to #522 ?

[larsks]

I don't think so. This stems from a problem I encountered where the module was failing with what should have been a valid username, and it turned out there were no spec tests for the username validation stuff.

[apenney]

Can you rebase this one for me? can't merge :(

[puppetcla]

CLA signed by all contributors.

[underscorgan]

@larsks ping?

[underscorgan]

Hi @larsks , thanks for the contribution. I think this is obsoleted by #635 so I'm going to close this for now, but that doesn't address all the validation you were hoping to have done, please resubmit with the additional work it needs. Thanks again!