Updated readme, vagrant configuration to include SBT, made other minor changes

The following changes were made:

* Readme updated to include instructions for SBT usage, storm deployment
* Vagrant box url edited to point to [Ubuntu Cloud Images Precise (12.04) current build](http://cloud-images.ubuntu.com/vagrant/precise/current/precise-server-cloudimg-amd64-vagrant-disk1.box)
* Vagrant config file updated to include SBT
* Vagrant config file updated so storm installs are idempotent
* Berksfile updated, maven removed