问rails 5.0.0.2不兼容和与gem mongoid的冲突

EN

    source 'https://rubygems.org'
# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '>= 5.0.0.beta2', '< 5.1'
#mongoid gem
gem 'mongoid', '~> 5.1.0'
# Use Puma as the app server
gem 'puma'
# Use SCSS for stylesheets
gem 'sass-rails', '~> 5.0'
# Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '>= 1.3.0'
# Use CoffeeScript for .coffee assets and views
gem 'coffee-rails', '~> 4.1.0'
# See https://github.com/rails/execjs#readme for more supported runtimes
# gem 'therubyracer', platforms: :ruby
# Use jquery as the JavaScript library
gem 'jquery-rails'
# Turbolinks makes following links in your web application faster. Read more: https://github.com/rails/turbolinks
gem 'turbolinks'
# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
gem 'jbuilder', '~> 2.0'
# Action Cable dependencies for the Redis adapter
gem 'redis', '~> 3.0'
# Use ActiveModel has_secure_password
# gem 'bcrypt', '~> 3.1.7'
# Use Capistrano for deployment
# gem 'capistrano-rails', group: :development
group :development, :test do
  # Call 'byebug' anywhere in the code to stop execution and get a debugger console
  gem 'byebug'
end
group :development do
  # Access an IRB console on exception pages or by using <%= console %> in views
  gem 'web-console', '~> 3.0'
  # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
  gem 'spring'
end
# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]

Bundler could not find compatible versions for gem "activemodel":
  In snapshot (Gemfile.lock):
    activemodel (= 5.0.0.beta2)

  In Gemfile:
rails (< 5.1, >= 5.0.0.beta2) was resolved to 5.0.0.beta2, which
depends on
activerecord (= 5.0.0.beta2) was resolved to 5.0.0.beta2, which
depends on
        activemodel (= 5.0.0.beta2)

rails (< 5.1, >= 5.0.0.beta2) was resolved to 5.0.0.beta2, which
depends on
activerecord (= 5.0.0.beta2) was resolved to 5.0.0.beta2, which
depends on
        activemodel (= 5.0.0.beta2)

    mongoid (~> 4.0.0) was resolved to 4.0.0, which depends on
      activemodel (~> 4.0)

    web-console (~> 3.0) was resolved to 3.1.1, which depends on
      activemodel (>= 4.2)