Nicht finden konnten, generator mongoid:config

Habe ich die folgende Fehlermeldung, wenn ich versuche, rails generieren mongoid:config
Nicht finden konnten, generator mongoid:config. Wenn ich angeben gem 'mongoid', '3.1.4', es gibt mir die folgende:

Bundler nicht finden konnte kompatible Versionen für die gem "activemodel": In
Gemfile:
mongoid (= 3.1.4) x86-mingw32 hängt
activemodel (~> 3.2) x86-mingw32

rails (= 4.0.0.rc2) x86-mingw32 depends on
  activemodel (4.0.0.rc2)

Bitte helfen. Danke!

GemFile:
gem 'rails', '4.0.0.rc2'

gem 'mongoid'
gem 'mongoid-paperclip'
gem 'bson_ext'

GemFile.lock

GEM

  specs:
    actionmailer (4.0.0.rc2)
      actionpack (= 4.0.0.rc2)
      mail (~> 2.5.3)
    actionpack (4.0.0.rc2)
      activesupport (= 4.0.0.rc2)
      builder (~> 3.1.0)
      erubis (~> 2.7.0)
      rack (~> 1.5.2)
      rack-test (~> 0.6.2)
    activemodel (4.0.0.rc2)
      activesupport (= 4.0.0.rc2)
      builder (~> 3.1.0)
    activerecord (4.0.0.rc2)
      activemodel (= 4.0.0.rc2)
      activerecord-deprecated_finders (~> 1.0.2)
      activesupport (= 4.0.0.rc2)
      arel (~> 4.0.0)
    activerecord-deprecated_finders (1.0.3)
    activesupport (4.0.0.rc2)
      i18n (~> 0.6, >= 0.6.4)
      minitest (~> 4.2)
      multi_json (~> 1.3)
      thread_safe (~> 0.1)
      tzinfo (~> 0.3.37)
    arel (4.0.0)
    atomic (1.1.9)
    bson (1.9.0)
    bson_ext (1.9.0)
      bson (~> 1.9.0)
    builder (3.1.4)
    climate_control (0.0.3)
      activesupport (>= 3.0)
    cocaine (0.5.1)
      climate_control (>= 0.0.3, < 1.0)
    coffee-rails (4.0.0)
      coffee-script (>= 2.2.0)
      railties (>= 4.0.0.beta, < 5.0)
    coffee-script (2.2.0)
      coffee-script-source
      execjs
    coffee-script-source (1.6.2)
    durran-validatable (2.0.1)
    erubis (2.7.0)
    execjs (1.4.0)
      multi_json (~> 1.0)
    hike (1.2.3)
    i18n (0.6.4)
    jbuilder (1.4.2)
      activesupport (>= 3.0.0)
      multi_json (>= 1.2.0)
    jquery-rails (3.0.1)
      railties (>= 3.0, < 5.0)
      thor (>= 0.14, < 2.0)
    json (1.8.0)
    leshill-will_paginate (2.3.11)
    mail (2.5.4)
      mime-types (~> 1.16)
      treetop (~> 1.4.8)
    mime-types (1.23)
    minitest (4.7.4)
    mongo (1.9.0)
      bson (~> 1.9.0)
    mongoid (1.0.6)
      activesupport (>= 2.2.2)
      durran-validatable (>= 2.0.1)
      leshill-will_paginate (>= 2.3.11)
      mongo (>= 0.18.2)
    mongoid-paperclip (0.0.8)
      paperclip (>= 2.3.6)
    multi_json (1.7.7)
    paperclip (3.4.2)
      activemodel (>= 3.0.0)
      activerecord (>= 3.0.0)
      activesupport (>= 3.0.0)
      cocaine (~> 0.5.0)
      mime-types
    polyglot (0.3.3)
    rack (1.5.2)
    rack-test (0.6.2)
      rack (>= 1.0)
    rails (4.0.0.rc2)
      actionmailer (= 4.0.0.rc2)
      actionpack (= 4.0.0.rc2)
      activerecord (= 4.0.0.rc2)
      activesupport (= 4.0.0.rc2)
      bundler (>= 1.3.0, < 2.0)
      railties (= 4.0.0.rc2)
      sprockets-rails (~> 2.0.0)
    railties (4.0.0.rc2)
      actionpack (= 4.0.0.rc2)
      activesupport (= 4.0.0.rc2)
      rake (>= 0.8.7)
      thor (>= 0.18.1, < 2.0)
    rake (10.0.4)
    rdoc (3.12.2)
      json (~> 1.4)
    sass (3.2.9)
    sass-rails (4.0.0.rc2)
      railties (>= 4.0.0.beta, < 5.0)
      sass (>= 3.1.10)
      sprockets-rails (~> 2.0.0)
    sdoc (0.3.20)
      json (>= 1.1.3)
      rdoc (~> 3.10)
    sprockets (2.10.0)
      hike (~> 1.2)
      multi_json (~> 1.0)
      rack (~> 1.0)
      tilt (~> 1.1, != 1.3.0)
    sprockets-rails (2.0.0)
      actionpack (>= 3.0)
      activesupport (>= 3.0)
      sprockets (~> 2.8)
    thor (0.18.1)
    thread_safe (0.1.0)
      atomic
    tilt (1.4.1)
    treetop (1.4.14)
      polyglot
      polyglot (>= 0.3.1)
    turbolinks (1.2.0)
      coffee-rails
    tzinfo (0.3.37)
    uglifier (2.1.1)
      execjs (>= 0.3.0)
      multi_json (~> 1.0, >= 1.0.2)

PLATFORMS
  x86-mingw32

DEPENDENCIES
  bson_ext
  coffee-rails (~> 4.0.0)
  jbuilder (~> 1.2)
  jquery-rails
  mongoid
  mongoid-paperclip
  rails (= 4.0.0.rc2)
  sass-rails (~> 4.0.0.rc2)
  sdoc
  turbolinks
  uglifier (>= 1.3.0)