added a guessCarrier utility method and added UPS detection.
added fedex and usps test cases for trk number variations
added test cases for amazon shipments
implemented regex for amazon shipments
implemented fedex 12, 15 digit and door tag check functions
added a test for fedex 20 digit, and also implemented smart post logic
implemented usps detection and added several more test cases
updated readme to provide instructions for guessCarrier()
coffeescript designation in readme
Merge pull request #11 from sailrish/sherlock

added ability to guess shipping carrier from tracking numbers