Update rvm.plugin.zsh

Ruby 2.1.1 -> Ruby 2.1.2.

plugins/rvm/rvm.plugin.zsh

@@ -6,7 +6,7 @@ alias gemsets='rvm gemset list'
 local ruby18='ruby-1.8.7'
 local ruby19='ruby-1.9.3'
 local ruby20='ruby-2.0.0'
-local ruby21='ruby-2.1.1'
+local ruby21='ruby-2.1.2'
 
 function rb18 {
 	if [ -z "$1" ]; then