Fix badges in README.

README.rst

@@ -1,5 +1,10 @@
-[![Build Status](https://travis-ci.org/dulwich/dulwich.png?branch=master)](https://travis-ci.org/dulwich/dulwich)
-[![Windows Build status](https://ci.appveyor.com/api/projects/status/mob7g4vnrfvvoweb?svg=true)](https://ci.appveyor.com/project/jelmer/dulwich/branch/master)
+.. image:: https://travis-ci.org/dulwich/dulwich.png?branch=master
+  :alt: Build Status
+  :target: https://travis-ci.org/dulwich/dulwich
+
+.. image:: https://ci.appveyor.com/api/projects/status/mob7g4vnrfvvoweb?svg=true
+  :alt: Windows Build Status
+  :target: https://ci.appveyor.com/project/jelmer/dulwich/branch/master
 
 This is the Dulwich project.