Updated latest supported Python3 to 3.4.0

Readme.md

@@ -44,12 +44,12 @@ Specify a Runtime
 You can also provide arbitrary releases Python with a `runtime.txt` file.
 
     $ cat runtime.txt
-    python-3.3.3
+    python-3.4.0
 
 Runtime options include:
 
 - python-2.7.6
-- python-3.3.3
+- python-3.4.0
 - pypy-1.9 (experimental)
 
 Other [unsupported runtimes](https://github.com/kennethreitz/python-versions/tree/master/formula) are available as well.