当我跑步时：

rails new blog

我得到：

Installing json (1.7.3)
Gem::InstallError: 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'
An error occurred while installing json (1.7.3), and Bundler cannot continue.
Make sure that `gem install json -v '1.7.3'` succeeds before bundling.

当我跑步时：

gem install json -v 1.7.3

我得到：

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'

我正在使用Windows 8 c:\ruby193\bin。我该如何解决这些错误？