If you are trying to run bundle install or rake version:write ib windows and receive the message The 'json' native gem requires installed build tools or 

Gem::InstallError: The 'json' native gem requires installed build tools.

Please update your PATH to include build tools 

you can resolve by doing the following:

Visit  

http://rubyinstaller.org/downloads

and download the development kit (make sure you download the link for the development kit, not ruby,etc) 

Once downloaded, follow the instructions on:

https://github.com/oneclick/rubyinstaller/wiki/Development-Kit