Add support for to_javascripts url property

1. Unprotect make_url.
2. Add simple delegator for model.url.
Also add support for javascripts.all

Add id, path and url as property of javascript object to allow mappings
to be rendered as well.
Missing change.
Add tests for javascript url features.
Typo in scenario

Should be
'And this file should have the fingerprinted javascripts "..."'
instead of
'And the file should have the fingeprinted javascript "..."'
Merge pull request #250 from richtera/urlSupport

Add support for to_javascripts url property