Update link to Windows installation guide

I've just released a new version of Run Jekyll on Windows and it's now got its own domain!
Merge pull request #2578 from juthilo/patch-1
Update history to reflect merge of #2578 [ci skip]
Fix Data Files example around iterative over files in a subfolder of _data.

Addresses @fkostadinov's comment in #2395:
https://github.com/jekyll/jekyll/pull/2395#issuecomment-48151478