fs-extra dependency causes problems

[yoz]

Because it's used inside a Nightmare action, fs-extra has to be resolvable from within nightmare, which means in npm 2 it gets very messy. The following is ok:

parent-package
- child-package
  - nightmare
  - nightmare-download-manager
  - fs-extra

This is not ok and results in MODULE_NOT_FOUND:

parent-package
- nightmare
- child-package
  - nightmare-download-manager
  - fs-extra

Yet this is ok:

parent-package
- nightmare
- fs-extra
- child-package
  - nightmare-download-manager

I'm not sure where things stand with npm v3 but I don't think devDependencies is the correct place for fs-extra in any case.

I'm honestly unsure where this should be fixed (in nightmare?) but it seems like the simplest workaround is to not use fs-extra inside of an action.

(Can we use fs-extra move() into the destination directory in the parent process rather than the child runner?)