Integer arguments to s3 options map

This makes using integer options passed to S3 methods more pleasant from the REPL.

pre this PR, cast to int was required...
```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....