Upgrade to rails 4

Upgraded the demo app to use rails 4.
Bug https://github.com/metaskills/less-rails/issues/95 meant that upgraded app initially just crashed - I had to work from a new rails 4.1.5 app and add the jquery-fileuplaod-rails-pareclip-example back in to isolate the cause which was due to a problem with the rubyracer.
The rest of the commits fix small glitches linked to the upgrade to rails 4