New Method: postalCodeCA

Checks for Canadian postal codes using the base regex from
http://geekswithblogs.net/MainaD/archive/2007/12/03/117321.aspx with
additional constraints from
http://www.canadapost.ca/tools/pg/manual/PGaddress-e.asp.
- First character must be a valid forward station character
- Must be all caps
- Must use space for forth character