-- Lots to do here
You might have installed rbenv/ruby-build in one of three ways (on OSX):
As a git repo (old method):
cd ~/.rbenv
git pull
rbenv install -l
rbenv install 2.1.1
Installed via Homebrew:
brew update
brew upgrade rbenv ruby-build
rbenv install -l
rbenv install 2.1.1
Installed with ruby-build as a plugin (currently the recommended way):
cd ~/.rbenv/plugins/ruby-build
git pull
rbenv install -l
rbenv install 2.1.1