There is a useful program for this called
nautilus-actions. This will let you customize the right-click menu. Just install it by using:
sudo apt-get install nautilus-actions
Launch it by using from the Ubuntu Dash menu (start searching for nautilus). It is called Nautilus-Actions Configuration Tool and has an icon the shape of a shell.
Nautilus Actions screenshot
It is quite easy to use, just use the add button in the top left-hand corner. Define the action (right-click menu's name) icon and terminal command along with a few other things.
For more information, follow the guide at https://askubuntu.com/a/88485/555667.