该捆绑包当前具有锁定在3.2.12的导轨。该怎么办？

我在gemfile中将rails版本从3.2.12更改为4.2.0

然后我得到这个错误：

The bundle currently has rails locked at 3.2.12

所以我尝试了bundle update /和bundle update rails ...但是我得到了这个：

Bundler could not find compatible versions for gem "rails":
  In Gemfile:
prototype-rails (>= 0) ruby depends on
  rails (~> 3.2) ruby

rails (4.2.0)

我需要做什么？

更新Gemfile：

source 'http://rubygems.org'
#gem 'rails', '3.2.12'
gem 'rails', '4.2.0'
gem "airbrake"
#gem "mysql"
gem 'mysql2',  '~>0.3.7'
gem 'fastercsv'
gem 'newrelic_rpm', :group => [:production, :staging]
gem "xml-simple", :require => "xmlsimple"
gem "will_paginate", "~> 3.0.0"
gem "json", '1.7.7'
gem "default_value_for"
gem "whenever"
gem 'charlock_holmes'
gem 'prototype-rails'
gem 'rails_autolink'

group :development do
  gem 'capistrano'
  gem 'capistrano-ext'
end