Prepare for 0.3.1 release

Author: Jesse Claven

setup.py

@@ -5,7 +5,7 @@
 
 setup(
     name="duffel-api",
-    version="0.3.0",
+    version="0.3.1",
     author="Duffel Engineering",
     author_email="[email protected]",
     description="Client library for the Duffel API",