Update README.md to use valid JavaSript dateString format.

I was noticing an issue with the localization of dates, and debugged the source of the issue to being the dateString in the md files.

Looking into it, all non-ISO format "short dates" should follow the following criteria (from http://msdn.microsoft.com/en-us/library/ie/ff743760(v=vs.94).aspx):

    - The format must follow the month/day/year order, for example "06/08/2010".
    - Either "/" or "-" can be used as a separator.