To install rvm you are going to need curl utility.
sudo apt-get install curl
RVM is the Ruby Version manager. To install rvm, use this command
curl -L https://get.rvm.io | bash -s stable
After you install rvm, you will see that you need to source rvm.
Now you should install rvm dependencies, in order work rvm properly
Get the latest version of ruby from their releases and install it with rvm and get it in use
rvm install ruby-2.2-head rvm use ruby-2.2-head