add rails runner alias

plugins/rails/rails.plugin.zsh

@@ -2,6 +2,7 @@ alias ss='thin --stats "/thin/stats" start'
 alias sg='ruby script/generate'
 alias sd='ruby script/destroy'
 alias sp='ruby script/plugin'
+alias sr='ruby script/runner'
 alias ssp='ruby script/spec'
 alias rdbm='rake db:migrate'
 alias sc='ruby script/console'