Automatically redirect to /{api version} if it's missing

I got bitten by the documentation saying that I could go to
http://localhost:8000/fields, and had a 404.

@Natim told me that instead of fixing the code, I could automatically redirect
to use the api version if the path is missing it.

If it's a bad idea, then it's @Natim's fault ;)

(Obviously, if it's a good idea, it's thanks to me, right? ;)
Thanks for using a 307 here :)