remove vendor directory for cedar-14

bin/steps/python

@@ -16,7 +16,7 @@ fi
 if [ ! $STACK = $CACHED_PYTHON_STACK ]; then
   bpwatch start uninstall_python
     puts-step "Stack changed, re-installing runtime"
-    rm -fr .heroku/python
+    rm -fr .heroku/python .heroku/python-stack .heroku/vendor
     unset SKIP_INSTALL
   bpwatch stop uninstall_python
 fi