Added support for date comparison in queries.  Enclose ISO formatted dates in query strings with ISODate() to signal they are dates.  E. g.:

...?query={"date" : {"$gte" : "ISODate(2013-12-31T13:59:59)"}}

The time portion of the date string is optional.
Merge pull request #45 from dvazquez1027/master

Added support for date comparison in queries.