I was wondering about the same thing, and while the online documentation is better because it is always up to date, I think that some people might benefit from an offline version - for example, I sometimes read it on the Tube. 
Here is the zip file, just unzip it all and open default.htm in your web browser:
The version is up to date as of 1/Jun/2014, though use it at your own risk, I cannot guarantee that all files are present, e.g. I removed the API folder since there is already a .chm reference.