Use rvm/ubuntu_rvm ppa for ubuntu distributions

[Kulgar]

As this ppa exists: https://github.com/rvm/ubuntu_rvm
And does quite nice things (quoted from rvm slack from @raelgc ):

the PPA has the rvm as a .deb file... is exactly the same rvm, but just in .deb format and using a mix install (global ruby, local gems)
the benefit is the automatic update, install rvm where Debian want it, and some old packages, like the libssl, when users want to install old rubies

It could be nice to use this ppa for ubuntu distributions instead of the rvm installer script: https://raw.githubusercontent.com/rvm/rvm/master/binscripts/rvm-installer

Or at least, to have an option to use that ppa instead of the installer script.

What do you think?

I could do some work on that task :-)