Integer arguments to s3 options map

This sits on top of my previous PR, and makes using integer options passed to S3 methods more pleasant from the REPL.

pre this PR
```clojure
(s3/list-objects cred bucket {:max-keys (int 10)})
```
Now...
```clojure
(s3/list-objects cred bucket {:max-keys 10})
```

Exceptions will still be raised it value is out of range, but that seems unlikely....