Authrequest date fix

[wesselej]

Ran into some problems with Microsoft ADFS server drifting out of sync with time server. Led me to find this issue with the time format. This change fixes the broken times generated as "2014-02-23T15:30:00Z" so that it says instead "2014-02-23T15:30:00GMT" (or whatever actual time zone the server is configured to).

I would have written a test to demonstrate this, but the code was buried in a way that did not lend it self to a direct test, and I didn't know if I should refactor the code just to allow for a test.

[Lordnibbler]

@wesselej can you please add specs if the refactor is straightforward?

[wesselej]

The refactor would have to set the time stamp (as a string) to a property of the Authrequest object, which could then be validated via a regular expression in the test. The variable would then be used to build the value of the XML request document instead of the method variable it's in now.

Alternatively, the test could just generate an XML request, parse the XML out with REXML or Nokogiri, find the value off the IssueInstant attribute and then validate it using a regex from there. Only after I sent the pull request did I think if this, but it still seems a like a lot of heavy lifting to do in the test, and I still think the refactor would be the better route to go.

[Lordnibbler]

Seems like a duplicate of #101

@wesselej Can you please write a test for this? 101 has gone stale and unanswered.

@luisvm @pitbulk @inakidelamadrid can you guys review?

[Lordnibbler]

handled via #138