Fix script newline escaping with expanded assets

If config.assets.debug = true is set, the jquery.ui.all.js is expanded
into several smaller required scripts. This means the
javascript_include_tag returns newlines that need to be escaped to
generate valid code. Without this using force: true in development
generates an Illegal Character parsing error.
Merge pull request #10 from felixbuenemann/fix-fallback-newline-escaping

Fix script newline escaping with expanded assets