Create texas_am.rb

My first open source contribution and first time writing ruby code. Let me if I didn't conform to the interface correctly. It works fine in Geocoder locally but I may have missed something important that I haven't encountered yet. Adding the results code next.

Texas A&M API calls require splitting up address, city, state, and zip. Instead of implementing clever functionality to intelligently determine each of these parameters in a raw string, I just assume a well-formed input of the form: <streetAddress>,<city>,<state>,<zip>. One or more of these parameters can be missing, but the commas are necessary to split up the query for the request. Let me know if you'd like this to be implemented differently.