Create rtorrent_installer.0.1.sh

I take no credit for the code here. All I have done is change a few 
of the options. The original of this script can be found here: 
https://github.com/Kerwood/rtorrent.auto.install

I do plan to add a few things and keep this up to date with the latest rutorrent and rtorrent releases.

Future plans include:
1. adding the option to install autodl-irssi plugin for rutorrent
2. adding multi user support