Error while installing RVM using Curl in Ubuntu 14.04
curl is used to download files via HTTP much like wget and it means that a connection to the remote site is failing which is why it is unable to download. Saw this on another forum, give it a shot and see if it works for you:
"replace the get.rvm.io part with raw.github.com/wayneeseguin/rvm/master/binscripts/rvm-installer -it's the same script, just takes out some potential DNS problems on rvm's end"
Refere to this link https://www.digitalocean.com/community/questions/how-to-install-ruby-on-rails