Added the Services_Twilio PEAR-compatible library. See CRM-12399 for more information.

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* CRM-12399: Integrate official Twilio PHP library with org.civicrm.sms.twilio
  http://issues.civicrm.org/jira/browse/CRM-12399
Merge pull request #13 from mmikitka/crm-12399-integrate-official-twilio-library

Added the Services_Twilio PEAR-compatible library. See CRM-12399 for more information