Proposed v1.0.0 with sophisticated lookup

To address issue #2 I've added mms address lookup.

Also, lookups are less sensitive. For example, the gateways for "AT&T" can be lookup by the string "AT&T Mobility" or simply "att".

The current functionality still works, but I didn't bother to document it, since it should be deprecated moving forward.

The only things that aren't 100% backwards compatible:

  * I updated some gateway addresses to the current addresses
  * `require('sms-address').carriers` gives a short name as a key (i.e. "verizon" instead of "Verizon Wireless"), but I can change that back if necessary.