Reorganize project structure.

Using gradle to "build" and test gw was a nice idea, but I think it will
be easier to structure the project this way and add a simple install.sh
script.
Minor script cleanup.
Squashed 'vendor/bats/' content from commit 2476770

git-subtree-dir: vendor/bats
git-subtree-split: 2476770c84df6f296adc9e4228af9cf9463c4458
Merge commit '8ba939d44ee8f5e01f0d67da99ad46272e4741e5' as 'vendor/bats'
Add an install script.

Shamelessly ripped off from bats (https://github.com/sstephenson/bats).
Add a license.
Overhaul the README.