I receive a compile error when trying to manually create this class in a development org. I set the API version to 29.0, because our org is not using version 30.0 yet. I was not able to create the Visualforce pages because I believe a few items in the page are dependent on this APEX class.
When I open this class in the Developer Console and try to save there is a 'problem' that says 'TwilioClientController' line 2 Invalid type: TwilioCapability.
I followed the previous steps including successfully installing the Twilio library (From Pull Request 33 on Twilio-Salesforce github).
I installed the Twilio library in both production and sandbox. I updated the link from login.salesforce.com to test.salesforce.com and left the remaining extension was able to successfully install Twilio library in development sandbox.