Allowing users to call with single click (skips the dialer)

I just tried out TextSecure for the first time today and was annoyed that I had a 2 step process in order to place a call from the conversation.

I am not sure if you guys intentionally didn't include this functionality (maybe you guys didn't want to add an extra permission). I did a quick search of the issues and didn't find anything, so sending a pull request to integrate this functionality.