ENFILE: file table overflow

There's a possibility for DocumentJS to attempt to open too many files, resulting in the: `Too many files open` issue. This is specific for Macs, but I imagine the limit exists in all OSs. Reference: http://superuser.com/questions/433746/is-there-a-fix-for-the-too-many-open-files-in-system-error-on-os-x-10-7-1

Scenario: A project with a `public` folder and its own `package.json`. Eg: `public/package.json` and `/package.json` both exist. As a result, DocumentJS will attempt to document all node modules as well(assuming we've forgotten to add this path to the `ignore` option in document.js).

Note: This issue is for discussion as it may not be DocumentJS's responsibility. However, as this is a tool that easily can scan a large part of the filesystem, we may want to institute some safeguards.

Reproduce the scenario with both a root package.json and public/package.json, then inspect how DocumentJS discovers and opens files while scanning node modules. Review whether safeguards are appropriate for the file-table overflow case across operating systems; the issue is currently framed for discussion, so completion criteria are not defined.

Written by the indexing model from the issue text.