升级Rails 4.0.0.rc2提示依赖问题

[breakliu]

Bundler could not find compatible versions for gem "railties":
  In Gemfile:
    bootstrap_helper (~> 4.2.2.1) ruby depends on
      railties (= 4.0.0.rc1) ruby

    railties (4.0.0.rc2)

[simlegate]

@xdite dependency should ~> 4.0.0.rc1