Bundler无法使用PayPal的adaptive_payments_samples

Question

尝试安装'adaptive_payments_samples'宝石时出现以下错误：https://github.com/paypal/adaptivepayments-sdk-ruby/tree/master/samples

我不确定我缺少什么宝石或者我应该解决什么依赖问题。 捆绑更新，但没有帮助。

Bundler could not find compatible versions for gem "rails":
  In snapshot (Gemfile.lock):
    rails (= 4.2.3)

  In Gemfile:
    rails-assets-cdn (>= 0) ruby depends on
      rails (>= 0) ruby

    rails-assets-cdn (>= 0) ruby depends on
      rails (>= 0) ruby

    griddler-mandrill (>= 0) ruby depends on
      griddler (>= 1.2.1) ruby depends on
        rails (>= 3.2.0) ruby

    adaptive_payments_samples (>= 0) ruby depends on
      rails (~> 3.2.9) ruby

    rails (~> 4.2.3) ruby

Running `bundle update` will rebuild your snapshot from scratch, using only
the gems in your Gemfile, which may resolve the conflict.