New Tags: dateTime

[neocotic]

As suggested by Jim Leis, it would be extremely useful if the date/time could be accessible via a new tag/tags.

This should be added as a function that will take a date format string and output the parsed current date/time. If the format string is invalid an error should be displayed. If no format string is provided (either empty or called as a simple tag) then a predefined format string will be used to parse the current date/time instead.

Embedded documentation will need to be updated.

[neocotic]

I'll use my new library, date.js, to handle this.

[neocotic]

I'll be delivering a fix for a bug introduced by #54 along with this as well as fix for a bug I noticed with mustache.js which prevented functions being called with no contents or as simple tags.