Hey zeke, I know you pulled his from #41, where I offered this as a one-liner solution, but if we're going to add a regex-based validate() method, it should conform as closely as possible to what RFC4122 does/doesn't allow.  Specifically:

* Allow upper case chars on input (http://tools.ietf.org/html/rfc4122#section-3, bottom of pg 2)
* Disallow non-hyphenated IDs (http://tools.ietf.org/html/rfc4122#section-3, top of pg 3)
* Disallow Ids with invalid version (http://tools.ietf.org/html/rfc4122#section-4.1.3) and variant (http://tools.ietf.org/html/rfc4122#section-4.1.1) fields

Thus, this regex:

    /[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-5][0-9a-fA-F]{3}-[89ABab][0-9a-fA-F]{3}-[0-9a-fA-F]{12}/