Fix Error: EMFILE, too many open files

When running jsxhint on all of my components like `jsxhint
path/to/components/**/*.jsx`, I am getting the following error:

> Error: EMFILE, too many open files

After some quick Googling, it looks like you can drop in graceful-fs as
a replacement for fs and this will go away.

http://stackoverflow.com/a/15934766/18986
https://github.com/isaacs/node-graceful-fs

Fixes #14