:memo: Document process for hacking node module components

See: http://discuss.atom.io/t/how-to-setup-development-for-core-modules-like-atom-keymap/9221/18?u=leedohm
Merge pull request #2240 from lee-dohm/node-module-doc

:memo: Document process for hacking node module components
Merge branch 'atom_master'