More pythonic way to pass args.

[hmacdope]

          Now that I think about it more pythonic would be to pass these as named args rather than a dict with an expected structure but we can discuss as is big API change.

Originally posted by @hmacdope in #38 (comment)

[kaminow]

yeah this makes sense and shouldn't be too difficult. I had it this way initially because that's how some of the underlying models expect the input, but I can just as easily package as a dict on the fly as unpackage for the other models