Added support for package manager installed rbenv.

plugins/ruby/init.zsh

@@ -12,10 +12,13 @@ if [[ -s "$HOME/.rvm/scripts/rvm" ]]; then
 
   # Source RVM.
   source "$HOME/.rvm/scripts/rvm"
-# Loads rbenv into the shell session.
+# Loads manually installed rbenv into the shell session.
 elif [[ -s "$HOME/.rbenv/bin/rbenv" ]]; then
   path=("$HOME/.rbenv/bin" $path)
   eval "$(rbenv init - zsh)"
+# Loads package manager installed rbenv into the shell session.
+elif (( $+commands[rbenv] )); then
+  eval "$(rbenv init - zsh)"
 else
   # Install local gems according to Mac OS X conventions.
   if [[ "$OSTYPE" == darwin* ]]; then