drop unused interface, mark override
change Column.ReadRange to return both an initial and an ongoing set of data
change range limit to Option[Long]
cosmetic
pass actor system around, might be useful someday
minor refactoring in RawTransform
interim work on notification between cassandra readers and writers

separate cassandra store into Reader vs. Writer interfaces
send notification on writes
. send Streams response over websocket using stream api, rather than http api
. cassandra reader now reports ongoing writes continuously
. add readFromStart method for half bounded ranges in cassandra (mostly untested)

all tests pass
Update message sending code compiles..
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