Rewrite rules for IIS #24

I'm unsure how to suggest an addition to the documentation, I hope as an issue isn't badly against etiquette.

Statcache rewrite rules for IIS are provided at the link below. Only files 02 and 03 are required. Key thing to note is IIS doesn't like the HTTP_USER_AGENT as 'MODX RegenCache' but is fine with just 'RegenCache'.

https://gist.github.com/chrisdempsey/768bc992bfffa8573382