Consistent headlines & ToC

I believe the topics and their headlines should be consistent for obvious reasons. Also

guides/source/working_with_javascript.md

@@ -5,11 +5,11 @@ This guide covers the built-in Ajax/JavaScript functionality of Rails (and
 more); it will enable you to create rich and dynamic AJAX applications with
 ease! We will cover the following topics:
 
-* Quick introduction to AJAX
+* An introduction to AJAX
 * Unobtrusive JavaScript
-* How Rails' built-in helpers assist you
-* Handling AJAX on the server side
-* The Turbolinks gem
+* Built-in Helpers
+* Server-side concerns
+* Turbolinks
 
 -------------------------------------------------------------------------------
 
@@ -246,7 +246,7 @@ this generates
 
 Since it's just a `<form>`, all of the information on `form_for` also applies.
 
-Server side concerns
+Server-side concerns
 --------------------
 
 AJAX isn't just client-side, you also need to do some work on the server