Merge pull request #1763 from jonilicious/master

RVM plugin - Fixes wrong variable used in 'rb20' function

plugins/rvm/rvm.plugin.zsh

@@ -31,7 +31,7 @@ compdef _rb19 rb19
 
 function rb20 {
 	if [ -z "$1" ]; then
-		rvm use "$ruby"
+		rvm use "$ruby20"
 	else
 		rvm use "$ruby20@$1"
 	fi