correct benchmark scripts

.gitignore

@@ -1,6 +1,6 @@
 /.bundle/
 /.yardoc
-/Gemfile.lock
+Gemfile.lock
 /_yardoc/
 /coverage/
 /doc/

benchmark/babel/Gemfile

@@ -5,6 +5,3 @@ if ENV['RR']
 else
   gem 'mini_racer', path: '../../'
 end
-
-gem 'execjs', github: 'rails/execjs'
-gem 'uglifier'

benchmark/babel/bench.rb

@@ -1,6 +1,6 @@
 unless defined? Bundler
   system 'bundle'
-  exec 'bundle exec bench.rb'
+  exec 'bundle exec ruby bench.rb'
 end
 
 require 'mini_racer'