更换淘宝源：

$ gem sources --add https://ruby.taobao.org/ --remove https://rubygems.org/$ gem sources -l*** CURRENT SOURCES ***https://ruby.taobao.org# 请确保只有 ruby.taobao.org$ gem install rails

https://ruby.taobao.org/

修改redmin路径下的Gemfile，然后使用bundle install安装

==============

安装redmine的webhook

cd $REDMINE_ROOT/plugins

git clone git://github.com/suer/redmine_webhook.git

bundle install

rake redmine:plugins:migrate RAILS_ENV=production

-------

报错：

You have already activated rake 10.0.2, but your Gemfile requires rake 11.1.1.

run

$ bundle update rake

that worked for me.

see the documentation. 

http://stackoverflow.com/questions/36024048/rails-getting-rake-error