Migrate from make to gulp. Resolves GH-143. Resolves GH-142.

Removed `makefile` and migrated build and test targets to `gulp`. Updated `README.md` to reflect changes.

`make build` ~> `gulp build`
`make test` ~> `gulp test`
`make dev` ~> `gulp watch`
`make serve` ~> `gulp server`

![](http://media.giphy.com/media/5bz02y39GDgju/giphy.gif)