Update README.md

Update the link to the documentation. All GitHub pages are now using the github.io domain.

README.md

@@ -4,7 +4,7 @@ jq
 jq is a command-line JSON processor.
 
 If you want to learn to use jq, read the documentation at
-[http://stedolan.github.com/jq](http://stedolan.github.com/jq). This
+[http://stedolan.github.io/jq](http://stedolan.github.io/jq). This
 documentation is generated from the docs/ folder of this repository.
 
 If you want to hack on jq, feel free, but be warned that its internals