Support 'C Spire' phone network for SMS. Fixes #1287

Adds support for the "cspire" cell carrier for user SMS
 notification options.

 Testing Notes:
 ==========
 NOTE: Full testing requires someone with that network service
 to verify that messages are correctly being received.
 * On /profile/settings page click the 'Add Contact Method'
    in the sidebar under "Other Contacts"
* On the "Text (SMS)" tab, verify that 'C Spire' is now a carrier
   option.
* Verify that when selected, the "SMS Email" uses the
   "@cspire1.com" domain

Change-Id: I1dd409f728cff28499bfbf5fa7c189f64f705746
Reviewed-on: https://gerrit.instructure.com/16555
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>
QA-Review: Marc LeGendre <marc@instructure.com>

app/models/communication_channel.rb

@@ -56,6 +56,7 @@ class CommunicationChannel < ActiveRecord::Base
         { 'AT&T' => 'txt.att.net',
           'Alltel' => 'message.alltel.com',
           'Boost' => 'myboostmobile.com',
+          'C Spire' => 'cspire1.com',
           'Cingular' => 'cingularme.com',
           'CellularOne' => 'mobile.celloneusa.com',
           'Cricket' => 'sms.mycricket.com',