Fix inset block

Had to revert my original changes into dough as my tests were running against an old Gemfile.lock so my tests were passing locally but failing CI. Changes are:

- The original inset block work
- Create symlink for "frontend-assets" as this is used by current live but breaks when integrating something outside of the responsive site
- Added sass-globbing gem to spec dummy. Although the docs suggest not to use it in Rails > 3.1 it resolves the problem where sass is not listening to the globbing import rules given
- I removed the basic css from spec dummy as it was causing problems. This can be investigated later