Make the API call for creating S3 bucket optional

[radeksimko]

The first time you access the S3 bucket, an extra request is being made to S3 which is in most cases useless.

https://github.com/qnub/django-boto/blob/master/django_boto/s3/storage.py#L42-45

    @property
    def bucket(self):
        if not self._bucket:
            self.s3 = connect_s3(aws_access_key_id=self.key, aws_secret_access_key=self.secret, host=self.host)

            try:
                self._bucket = self.s3.create_bucket(self.bucket_name, location=self.location, policy=self.policy)
            except (S3CreateError, S3ResponseError):
                self._bucket = self.s3.get_bucket(self.bucket_name)
        return self._bucket

I understand that the original reason might have been to make it more convenient by not having to go to AWS console and creating the bucket there but there should be a way how to turn this off and maybe even not doing it by default (that might be arguable).

You might not always value the convenience over performance & costs (though I know the cost per request is very low, it's not zero exactly because of preventing doing things like this).