Added a plugin that adds autocomplete to the adhearsion gem

This adds autocomplete for [adhearsion](https://github.com/adhearsion/adhearsion), a Ruby framework for creating telephone applications.

![base autocomplete](http://i.imgur.com/WE0WBKE.png)
![2nd level autocomplete](http://i.imgur.com/v8YCNCE.png)