I wrote a shell script that can automate ruby on rails framework installation or Ubuntu , You have to just Download and execute that script . this script will check and download all require components and dependencies . that script use RVM to install ruby and rails gem . 

By default with will install

1. rvm
2. ruby 2
3. rails 4

setup

$ wget -qO- https://raw.github.com/alokyadav15/rinstaller/master/rails.sh | bash

on any kind of download error

try with

$ wget --no-check-certificate https://raw.github.com/alokyadav15/rinstaller/master/rails.sh
$ chmod +x rails.sh
$ ./rails.sh

All suggestions all most welcome , fork that on github

Github Repo :  https://github.com/alokyadav15/rinstaller