Upgrade slick to 2.1.0

Also contains some starts to refactors. Making this PR now as to match up with the upgrade to slick 2.1.0 in GeoTrellis and the gtfs-parser project.

Feel free to ask questions about the work-in-progress refactor on this PR. I'm making comments to point out a couple of things that I changed.
the `geotrellis 0.9.1` dependency wasn't being used, was just being used to pull in Akka, so I pulled in Akka directly.