Add date formatting for datetime etc instances

[GoogleCodeExporter]

It's useful to be able to specify a format for datetime values. I've attached a 
diff that provides this functionality, basically by copying the float and int 
formatting. It's applied to any object with a "strftime" method, which catches 
date, time and datetime.

The validation of the format is pretty minimal, because you can put basically 
anything in a strftime format. I wondered whether it was worth it, but I left 
it as it's easier to extend the checks in the future if needed.

Original issue reported on code.google.com by p.f.mo...@gmail.com on 28 Aug 2014 at 1:31

Attachments:

• prettytable.diff