Use the ActiveMerchent luhn_check and brand methods
remove requiring rubygems
remove activemerchent dependency and bring in the regexs
A few nitpicks
Use the map used in ActiveMerchant for easier maintanance
Do not compile company prefix regexp on each sanitize involcation
Merge pull request #16 from zendesk/vkmita/check-if--actually-a-cc

Use the ActiveMerchant company specific credit card regexes