Restore original comment about node_modules

It's not the opinion of "some people", it's a conditional circumstance.
Even proponents of checking node_modules into Git agree that you
shouldn't do it when you're writing a module to be included as a
dependency on npmjs.org: the advantage of checking node_modules
into Git is only for fully-packaged apps, which is why the original
comment was what it was.
Let node_modules FAQ URL speak for itself
Merge pull request #1233 from stuartpb/patch-1

Restore original comment about node_modules