Make it play better with Jest's options

[rogeliog]

The way for customize jest-runner-mocha is through an extra config file(jest-runner-mocha.config.js), which I really dislike.

It would be awesome to make it work out of the box with several Jest options... coverage and transform would be amazing

In an ideal world one could do the following

yarn add --dev jest babel-jest jest-runner-mocha

and then run

yarn jest -- --coverage

and it should just work