Added date support for ISO 8601 to default culture (now with new and improved tests!)

G'day mate,

RE: Your question in my previous pull request https://github.com/jquery/globalize/pull/122

By adding it to the default culture it will then work for all cultures.  I.e. specific cultures extend and override the default culture.  It made the most sense to me for it to work for all cultures given that its an international standard.  Is that cool with you?

I also thought I should add some tests, apologies for not doing it in the first instance like I really should have.  I balked at first, because by virtue of the fact the ISO format includes an offset, the expected value changes based upon the current offset of your computer's system time.  I ending up working out a way to account for this simply enough, this is what the offsetDelta function is doing.

I hope you don't mind, but I also did a tiny bit of tidying up of some of the existing tests.  There was a parse.js file containing tests for the "parseFloat" module and within this module there were also tests related to the parsing of dates.  Therefore I renamed parse.js to match its module name and introduced a parseDates.js file/module to contain the existing date parse tests along with the new ISO8601 tests.

By the way, apologies for creating a new PR, Github automatically closed the previous one when I did a force push to reset back to the initial state so that I could do some cleanup before introducing the new format. (I'm a Github newbie - my first... well I suppose second ever pull request)

Any further questions give me a yell!


Cheers,
Dan.