Add regex format for Canadian postal codes

Another relatively straightforward one, [data from here](http://i18napis.appspot.com/address/data/CA). [Wikipedia](http://en.wikipedia.org/wiki/Postal_codes_in_Canada) backs up the format (e.g. `A1A 1A1`), with a few caveated letters.

__Proposed format__
`^[ABCEGHJKLMNPRSTVXY]\d[ABCEGHJ-NPRSTV-Z][ ]?\d[ABCEGHJ-NPRSTV-Z]\d$`

__Examples__
- H3Z 2Y7
- V8X 3X4