[requirejs] fix regexp for specs paths

I am not sure if someone has tested it but it doesn't work for me. In development, my path looks like this:
```
app/assets/javascript/application.js?body=1
```
As you may see here: http://rubular.com/r/cNDqtMo50Y it doesn't match properly (you can compare with the new version: http://rubular.com/r/fhrXbcszJx)