Cannot resolve gem dependencies - doorkeeper, sass-rails - on jruby using Rails 4

I have googled around a lot to find answers and cannot find one. How do I resolve this dependency issue. If I remove sass-rails (which isn't practical but just for testing issues) then the problem just rolls down the Gemfile to coffee-rails having the dependency conflict.

Bundler could not find compatible versions for gem "railties":
  In Gemfile:
    doorkeeper (~> 0.6.7) java depends on
      railties (~> 3.1) java

    sass-rails (~> 4.0.0.beta1) java depends on
      railties (4.0.0.beta1)

I have tried deleting the Gemfile.lock and redoing the bundle install. No joy.

I checked applicake/doorkeeper issues on GitHub. This gem does not support Rails 4 yet, and 0.6.x will not support.

https://github.com/applicake/doorkeeper/pull/200

We won't plan to support versions less than 1.0 for rails 4.

But someone already forked for Rails 4 like this https://github.com/applicake/doorkeeper/pull/213 .
You can use these forks as below.

# Gemfile
gem 'doorkeeper', github: 'kaznum/doorkeeper', branch: 'support_rails4'

Hope to help you.