Added list of external packages required and a script to install them all

Pull request:
if someone with a working ros-hydro-distro could make sure this works by:
1. checking out this branch.
2. running the install script
3. Making sure it completes sucessfully
4. Spinning up the roscore and then trying to run one of the nodes from newly installed packages (e.g, joy joy_node)
5. If this works, we're all set; merge the pull request