Chapter 1 of gradle userguide at the end

The current userguide seems to be broken. Chapter 1 of the single userguide is at the very end of the document.

http://www.gradle.org/docs/current/userguide/userguide_single.html#introduction

I really think that it is not meant to be like this. So I push this a bit.

Raised as GRADLE-2893.