Tries to revive Date types from the JSON

[etiago]

I didn't write tests yet as I wanted to brainstorm about this with the developers first. This relates to issue #68 and tries to fix it by using a reviver when parsing the JSON to try and revive any string as a Date. Unfortunately there doesn't seem to be a better option in Javascript.

[msftclas]

All CLA requirements met.

[damccorm]

While I see why this might be useful, I'm concerned about a couple things. First, and most importantly, it seems like this could cause serious issues with backwards compatibility - if people are expecting a string and that suddenly shifts to a date that would cause problems. Second, albeit less importantly, this could cause issues with strings that look like dates but aren't meant to be dates.

Overall, it seems to me that this has the potential to cause more issues than its worth, especially since you should be able to just manually do the conversions on your end without too much trouble.