Install RBEnv on OSX/Linux

RBEnvInstall.sh

# Download RBEnv
git clone git://github.com/sstephenson/rbenv.git $HOME/.rbenv

# Find out which shell init file exists.
if [ -f $HOME/.zshrc ]
then
  SHELL_INIT="$HOME/.zshrc"
elif [ -f $HOME/.bashrc ]
then
  SHELL_INIT="~/.bashrc"
elif [ -f $HOME/.bash_profile ]
then
  SHELL_INIT="$HOME/.bash_profile"
else
  echo "No shell init!"
fi

cat << EOF >> $SHELL_INIT
export RBENV_ROOT=$HOME/.rbenv
export PATH="${RBENV_ROOT}/bin:$PATH"
eval "$(rbenv init -)"
EOF

# Download rubybuild
git clone https://github.com/sstephenson/ruby-build.git $HOME/.rbenv/plugins/ruby-build

# Never run `rbenv rehash` again!
git clone https://github.com/sstephenson/rbenv-gem-rehash.git $HOME/.rbenv/plugins/rbenv-gem-rehash

echo "RBEnv installed!"