Merged class Drop into DropController

closes #112.

* Moved functions from Drop.java into DropController.java
* Deleted Drop.java
* Renamed DropTest.java to DropControllerTest.java
If this is all (besides calling ```drop.sendAndForget(dropMessage, contact)```) a user of the drop package needs to do to send a drop message this is really cool. No generics for the user (i.e. module developer) anymore :)