FileGlobs: Extract ignore globs from .npmignore file

Some developers use `.npmignore` file to keep stuff out of their npm package. If there's no `.npmignore` file, but there is a `.gitignore` file, then npm will ignore the stuff matched by the `.gitignore` file.

Like git, npm looks for `.npmignore` and `.gitignore` files in all subdirectories of your package, not only the root directory. (There's an issue https://github.com/coala/coala-quickstart/issues/108 for this functionality)

`.npmignore` files follow the same pattern rules as `.gitignore` files.

difficulty/low