redmine3.2へpluginのbacklog1.0.0をインストールしようとすると下記のエラーが出ます。
解決策をおしえていただけますでしょうか。よろしくお願いします。

[root@localhost redmine]# bundle exec rake redmine:backlogs:install

[!] There was an error parsing `Gemfile`: 
[!] There was an error parsing `Gemfile`: You cannot specify the same     gem twice with different version requirements.
You specified: nokogiri (>= 1.6.7.1) and nokogiri (>= 0). Bundler     cannot continue.

 #  from /var/www/redmine/plugins/redmine_backlogs/Gemfile:13
 #  -------------------------------------------
 #  gem "icalendar"
 >  gem "nokogiri"
 #  gem "open-uri-cached"
 #  -------------------------------------------
. Bundler cannot continue.

 #  from /var/www/redmine/Gemfile:113
 #  -------------------------------------------
 #  Dir.glob File.expand_path("../plugins/*/{Gemfile,PluginGemfile}", __FILE__) do |file|
 >    eval_gemfile file
 #  end
 #  -------------------------------------------

追記

Gemfileを修正してgem "nokogiri", "=>1.6.7.1"にするとどうでしょうか。

参考）
https://github.com/Hopebaytech/redmine_mail_reminder/issues/58

上記のよう修正しましたらまた違うエラーがでてしました。 

 [picolit@localhost redmine]$ bundle exec rake redmine:backlogs:install
 Could not find gem 'capybara (~> 1.1.0)' in any of the gem sources
 listed in your Gemfile or available on this machine. Run bundle
 install to install missing gems.