Add Ting as a Provider

Confirmation from Ting agent that this is supported:
https://help.ting.com/hc/communities/public/questions/203771568-Can-you-send-a-text-message-to-a-phone-number-via-the-internet-email-

lib/providers.js

@@ -3,6 +3,7 @@ module.exports = {
   us: [
     '%s@email.uscc.net',
     '%s@message.alltel.com',
+    '%s@message.ting.com',
     '%s@messaging.sprintpcs.com',
     '%s@mobile.celloneusa.com',
     '%s@msg.telus.com',