Summary:
Adds two new template functions:
* `simpledate` formats recent dates in a human-friendly way, for example `Today
at 12:00`, `Wednesday at 07:30`, or `Jan 05 at 23:45`. The timezone used
can be overridden.
* `smartdate` shows different results depending on whether a date is recent
or not, where "recent" is defined by a threshold parameter.
Reviewed By: quark-zju
Differential Revision: D7123734
fbshipit-source-id: 7b68207e4debc85c0bfa72bba9b375a4aa11d7c6
