move sagemaker_s3_output to model class

[ChoiByungWook]

Issue #, if available:
#554

Description of changes:
Moved sagemaker_s3_output to model class.

There was a dependency error, in that a file in the local directory was taking dependency on a file in the rl directory.

I could have also allowed the rl directory to be properly scoped so that all directories have access, however that doesn't seem like the right call, as parameters and what not should be generic and not specific.

Reproduced customer error on a notebook instance and installed changes and tested properly.

It is difficult to write a test that catches this, as there seems to be weird interaction with tox and how our tests import classes. For now this is a quick fix.

Refactoring these parameters to a common class in the sagemaker directory might make things a little easier to manage.

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