Use 'application.js' in integration test

Instead of manually concatenating the individual files. The downside to
this is that we have to include all the comments already present in
‘application.js’.
Wrap javascript files in a CommonJS 'wrapper'

The wrapper captures the path of the file and injects `require`,
`exports`, and `module` into it.

Also updates the integration test for this. Before that test, we have
to capture the file paths.