clean up rails plugin, removing bundler-specific logic

plugins/rails3/rails3.plugin.zsh

 # Rails 3 aliases, backwards-compatible with Rails 2.
 
-function _bundle_command {
-  if command -v bundle && [ -e "Gemfile" ]; then
-    bundle exec $@
-  else
-    $@
-  fi
-}
-
 function _rails_command () {
   if [ -e "script/server" ]; then
     ruby script/$@
@@ -25,6 +17,3 @@ alias rp='_rails_command plugin'
 alias rs='_rails_command server'
 alias rsd='_rails_command server --debugger'
 alias devlog='tail -f log/development.log'
-
-alias rspec='_bundle_command rspec'
-alias cuke='_bundle_command cucumber'