Use --no-rehash option for faster startup

plugins/rbenv/rbenv.plugin.zsh

@@ -17,7 +17,7 @@ for rbenvdir in "${rbenvdirs[@]}" ; do
     FOUND_RBENV=1
     export RBENV_ROOT=$rbenvdir
     export PATH=${rbenvdir}/bin:$PATH
-    eval "$(rbenv init - zsh)"
+    eval "$(rbenv init --no-rehash - zsh)"
 
     alias rubies="rbenv versions"
     alias gemsets="rbenv gemset list"