Remove unnecessary titles

guide/introduction.md

@@ -1,9 +1,6 @@
 Introduction
 ============
 
-Purpose
--------
-
 Cowboy is a small, fast and modular HTTP server written in Erlang.
 
 Cowboy aims to provide a complete HTTP stack, including its derivatives

guide/routing.md

@@ -1,9 +1,6 @@
 Routing
 =======
 
-Purpose
--------
-
 Cowboy does nothing by default.
 
 To make Cowboy useful, you need to map URLs to Erlang modules that will