Removes references to Gizmo (R.I.P), adds CancelCall and getVoicemailMP3 functions.
Removes references to Gizmo (R.I.P), adds CancelCall and getVoicemailMP3 functions.

Removes references to Gizmo (killed by Google - R.I.P.)
Adds cancelCall function to cancel an in-progress call
Adds getVoicemailMP3 function to get MP3 file of voicemail
DanielMarquard/Google-Voice-PHP-API,aaronpk/Google-Voice-PHP-API