Rails 5 support

[biske]

I started upgrade to Rails 5 and after starting application it breaks execution with message:
`rescue in block (2 levels) in require': There was an error while trying to load the gem 'use_tinymce'. (Bundler::GemRequireError)
Gem Load Error is: use_tinymce has not been tested for this version of Rails: 5.0.0.1

Any plan to add support for Rails 5?
What is your opinion on effort to add it, maybe I can submit PR.