firien/tracking_number — pull request #1 by ilude (2014-04-30 18:01:38+00:00)
Title: add dhl and ontrac uri's, add base uri 

Since jkeen is not maintaining the uri feature, I'm sending this your way.

Adds DHL and OnTrac uri methods as well as an empty uri method to the base TrackingNumber class to prevent method not found errors.