Add a build step

We need this because we have JSX in our shapes. We want to keep that so
the tradeoff is the build step. Luckily this makes it so that you can
still npm install path/to/here directly.

- uses Gulp because it's a couple lines and I knew what I was doing
- builds files to lib/ and uses those everywhere. src/ is now excluded
- changes requires in the shapes to use ./ReactART
- updates ignores appropriately