Typescript support

[slashmobilitysl]

It would be nice if you added a typing for this plugin, to be used with Typescript (for instance, in a Angular 2 app).

I made a gist here containing mine, but I don't know where/how do you want to keep it in your repo.

[macdonst]

@slashmobilitysl why don't you add it to https://github.com/DefinitelyTyped/DefinitelyTyped and when your PR is accepted let us know and we'll add it to the docs here.