Utilize importable gulp tasks

**This is dependent upon on https://github.com/OneJSToolkit/gulp-onejs-compiler/pull/4 being merged**

Utilize the shared gulp tasks, just look at how much shorter our gulp file is now!

Also, changed `definitions` dir to be `typings` dir so that we can utilize https://github.com/DefinitelyTyped/tsd as a standard for importing tsd files (it's basically bower/npm for .d.ts files)