Merge pull request #1 from bkford/master

Made changes to core structure; added comments.
Merge pull request #2 from bkford/master

Updated core functionality and comments, improved code flow.
Merge pull request #3 from bkford/master

Before, the 'ChannelLeftBridge' event listener was being registered
multiple times. These changes fixed the issue by only registering
the event one time for each bridge. Now, the playbacks occur at the
desired time, instead of happening in incrementing amounts.

Relocated event listener to only register once
Playbacks occur reliably now, and as expected
MusicOnHold Functionality Added

Added music on hold functionality when there is one channel alone in the conference. When a channel joins the mixing bridge they are played MoH, but it stops when another channel joins the bridge. Also if there are multiple people in the bridge and everyone, besides one person, decides to leave then that one person left in the bridge will hear MoH.
Added db functionality.

All configuration options should be pulled from the database, not
the app itself. Therefore, we added postgreSQL to store our data.
Work in progress.

Later: make the code more "pretty"; move database side of the app
to its own section, separate from the rest of the code.

* Added postgreSQL db to the app
* Configuration options now available via psql!