Create ubuntu_oneclickinstall.sh

One click webogram installer script for ubuntu-based linux-distro's. 
Executes the folowing steps:
1) install nodejs
2) download the webogram zip from github
3) extract files and place them in /opt
4) create a launcher script in /usr/local/bin
5) create a menu item to launch webogram
Feedback on installer script.
Typo fix.
On Ubuntu 12.04 nodejs is not, it is called node.

Also install the .desktop file in /usr/share/applications since we are installing the script in /opt and not in $HOME
Small changes, we don't need to cd into /opt/webogram.