Change headings to markdown

README.md

@@ -1,4 +1,4 @@
-== Quick start ==
+# Quick start
 
 This is a lightweight C++ option parser library, supporting the standard GNU
 style syntax for options.
@@ -44,7 +44,7 @@ it appeared, and
 to get its value. If "opt" doesn't exist, or isn't of the right type, then an
 exception will be thrown.
 
-=== Positional Arguments ===
+## Positional Arguments
 
 Positional arguments can be optionally parsed into one or more options. To set up positional arguments, call 
 
@@ -52,17 +52,17 @@ Positional arguments can be optionally parsed into one or more options. To set u
 
 where "last" should be the name of an option with a container type, and the others should have a single value.
 
-== Linking ==
+# Linking
 
 This is a header only library.
 
-== Requirements ==
+# Requirements
 
 The only build requirement is a C++ compiler that supports C++11 regular 
 expressions. For example GCC >= 4.9 or clang with libc++.
 
 
-== TODO list ==
+# TODO list
 
 * Allow unrecognised options.
 * Various help strings.