Make 'test' the default gulp task

The referenced 'run' does not currently exist.

I'm shamelessly stealing your `gulp-setup` structure for another project; figured the least I owe for that is this minor cleanup.

I'm also a sucker for good build tool documentation, so I'm using [https://www.npmjs.org/package/gulp-help](gulp-help).  Any interest in a pull request that provides that here too?