Change Installfest to use rbenv rather than RVM?

[scottschup]

This may be something the people have Strong Opinions™ about, but since rbenv is more lightweight than RVM and is installable via HomeBrew making the initial install process much easier, it may be the better option for those new to Ruby/Rails.

There are also comparable version management systems for Python (pyenv) and Node (nodenv) that use similar syntax, whereas Python has no equivalent to RVM (that I know of).