Adding headroom.css

Description: A collection of CSS3 powered hover effects to be applied
to call to actions, buttons, logos, featured images and so on.
Source: https://github.com/IanLunn/Hover
Author: Ian Lunn
License: MIT
Fixed package.json
Added dropbox.js 0.10.3.
Merge pull request #3363 from JGallardo/master

Adding hover.css
Merge pull request #3366 from pwnall/db0103

Update dropbox.js to 0.10.3
npm auto-update for dropbox.js.
Merge pull request #3367 from pwnall/db_npm

npm auto-update for dropbox.js.
Updated packages via auto-update.js