Require modules as exercises.

Example Usage:

```js
var lorem = require('lorem-ipsum')
var exercise = require('workshopper-exercise')()
exercise = require('workshopper-boilerplate')(exercise)
exercise = require('workshopper-exercise/require')(exercise)

exercise.addBoilerplate(require.resolve('./boilerplate/hello_world.js'))

exercise.addSetup(function(mode, cb) {
  exercise.submissionArgs = exercise.solutionArgs = lorem().split(' ')
  cb()
})

module.exports = exercise
```