Remove opinion from Node.js .gitignore file

This is a PR to remove the opinionated lines from the Node.js .gitignore file.

I do not believe that Github's pre-baked .gitignore files should be promulgating opinions, especially in a community that is as fresh as the Node.js community.  Questions of what should be checked in should be a decision made on an organization-by-organization basis, or left up to the individual.  Github's inclusion of opinion in these files puts unnecessary authority behind that opinion, which can have the negative side-effect of people following without thinking.