我已经安装了Ruby 2.0.0以及rails 3.1.12。我正在尝试启动我的服务器，但最终出现以下错误：

Question

ERROR:  Error installing json:
        The 'json' native gem requires installed build tools.

Please update your PATH to include build tools or download the DevKit
from 'http://rubyinstaller.org/downloads' and follow the instructions
at 'http://github.com/oneclick/rubyinstaller/wiki/Development-Kit'

我尝试了许多答案，例如遵循wiki的devkit步骤，但我陷入了“ruby dk.rb install”步骤。我在config.yml文件中包含了ruby安装路径，然后错误仍然存​​在。

我还修改了环境变量以包含路径。然后我也失败了。

请帮我解决这个问题。

我的config.yml文件如下所示：

# This configuration file contains the absolute path locations of all
# installed Rubies to be enhanced to work with the DevKit. This config
# file is generated by the 'ruby dk.rb init' step and may be modified
# before running the 'ruby dk.rb install' step. To include any installed
# Rubies that were not automagically discovered, simply add a line below
# the triple hyphens with the absolute path to the Ruby root directory.
#
# Example:
#
# ---
# - C:/ruby19trunk
# - C:/ruby192dev
#
---