Additional gems to prevent some issues

I tried to generate new Rails 4 app and added the 'semantic-ui-rails' gem. It lead me to this error:
WARN: tilt autoloading 'less' in a non thread-safe way; explicit require 'less' suggested.
After I add gem 'less-rails' it worked ok.

gem 'therubyracer', platforms: :ruby added because it was an error with v8 library.