Build

This pull request is based on #25, as soon as that has been merged, I'll rebase out the extra commit. What this does:

- Adds a `package.json` file that includes gulp and dependencies
- Adds a Gulpfile with two tasks, one to umd-wrap the unminfied version and one to umd-wrap and minify a new version
- Adds the `dist` folder, which contains built versions of the scripts

One potential addition would be to pull out the header and add this through the build process, with a plugin like [gulp header](https://github.com/godaddy/gulp-header).

Closes #26