Adding JavaScript runtime to prevent errors

Since this is an example application, it should work out of the box without error. Without a defined JavaScript runtime, simply pulling the repository and attempting to run a rails generator fails:
```rails
[thoraxe@t510dora rails-example]$ rails g controller welcome
/home/thoraxe/.gem/ruby/1.9.1/gems/execjs-1.4.0/lib/execjs/runtimes.rb:51:in `autodetect': Could not find a JavaScript runtime. See https://github.com/sstephenson/execjs for a list of available runtimes. (ExecJS::RuntimeUnavailable)
        from /home/thoraxe/.gem/ruby/1.9.1/gems/execjs-1.4.0/lib/execjs.rb:5:in `<module:ExecJS>'
        from /home/thoraxe/.gem/ruby/1.9.1/gems/execjs-1.4.0/lib/execjs.rb:4:in `<top (required)>'
        from /home/thoraxe/.gem/ruby/1.9.1/gems/coffee-script-2.2.0/lib/coffee_script.rb:1:in `require'
        from /home/thoraxe/.gem/ruby/1.9.1/gems/coffee-script-2.2.0/lib/coffee_script.rb:1:in `<top (required)>'
        from /home/thoraxe/.gem/ruby/1.9.1/gems/coffee-script-2.2.0/lib/coffee-script.rb:1:in `require'
        from /home/thoraxe/.gem/ruby/1.9.1/gems/coffee-script-2.2.0/lib/coffee-script.rb:1:in `<top (required)>'
        from /home/thoraxe/.gem/ruby/1.9.1/gems/coffee-rails-3.2.2/lib/coffee-rails.rb:1:in `require'
        from /home/thoraxe/.gem/ruby/1.9.1/gems/coffee-rails-3.2.2/lib/coffee-rails.rb:1:in `<top (required)>'
        from /home/thoraxe/.gem/ruby/1.9.1/gems/bundler-1.3.5/lib/bundler/runtime.rb:72:in `require'
        from /home/thoraxe/.gem/ruby/1.9.1/gems/bundler-1.3.5/lib/bundler/runtime.rb:72:in `block (2 levels) in require'
        from /home/thoraxe/.gem/ruby/1.9.1/gems/bundler-1.3.5/lib/bundler/runtime.rb:70:in `each'
        from /home/thoraxe/.gem/ruby/1.9.1/gems/bundler-1.3.5/lib/bundler/runtime.rb:70:in `block in require'
        from /home/thoraxe/.gem/ruby/1.9.1/gems/bundler-1.3.5/lib/bundler/runtime.rb:59:in `each'
        from /home/thoraxe/.gem/ruby/1.9.1/gems/bundler-1.3.5/lib/bundler/runtime.rb:59:in `require'
        from /home/thoraxe/.gem/ruby/1.9.1/gems/bundler-1.3.5/lib/bundler.rb:132:in `require'
        from /home/thoraxe/Red Hat/ose/rails-example/config/application.rb:7:in `<top (required)>'
        from /home/thoraxe/.gem/ruby/1.9.1/gems/railties-3.2.13/lib/rails/commands.rb:24:in `require'
        from /home/thoraxe/.gem/ruby/1.9.1/gems/railties-3.2.13/lib/rails/commands.rb:24:in `<top (required)>'
        from script/rails:6:in `require'
        from script/rails:6:in `<main>'

This pull request adds "therubyracer" which is a JavaScript runtime. The addition prevents these errors.