Added validation for Draft 3 "format" values.

Hi Julian,

I've added some validation for the following values in "format" properties according to JSON Schema Draft 3:
 * date-time
 * date
 * time
 * utc-millisec
 * uri
 * email
 * ip-address
 * ipv6
 * host-name
 * color

I've also added some tests to test them (and show the limitations of the regular expressions I've used for validation of "ip-address", "ipv6", "host-name" and "color").

Let me know if there is anything you'd like me to change, or think I could improve.

Cheers