setup of definition files for module.utils

Added typescript definition. Can be used with function `tsd link` to directly add definition file to tsd.d.ts of requiring projects
I know you mention it in the PR description, but perhaps it could be worthwhile to describe the whole workflow (`tsd` @ dev, `tsd-link`, `tsd link` and how they all work together, and in combination with `npm link`) somewhere in the wiki?