Allow alternate python installation locations

My python path is sometimes /usr/local/bin/python, sometimes in some fun virtualenv.

Using `/usr/bin/env python` lets these scripts for provisioning not care.

Note: In order to use this, I also deleted `ansible_python_interpreter` from `inventory/provision` (not included as part of this PR):

```
diff --git a/inventory/provision b/inventory/provision
index c06fdd3..6e9d5f3 100644
--- a/inventory/provision
+++ b/inventory/provision
@@ -24,5 +24,5 @@ proxy
 management

 [local]
-localhost ansible_connection=local ansible_python_interpreter=~/bin/Pythonic
+localhost ansible_connection=local
```