Move date formatting to the client side

This PR moves the majority of date formatting (relative and standard) to the client side using moment, taking a *tiny* bit of load off, but most importantly, removing unrequired code.

No new unit tests have been added, as they aren't required, but all the existing tests still pass.

If moment is unavailable, or the browser does not support it, it simply falls back to `{Mfull} {D}, {YYYY}` (eg. August 31, 2014).

I've added the dependency `Timex` by @bitwalker to generate both ISO-8601 dates (for Moment) and `{Mfull} {D}, {YYYY}` dates (for a fallback)