Add some WireFormats and helpers
Add an integration test

Whew! That got a bit ugly.

I can't warrant against memory leaks / etc, but this seems to complete
reliably.

Next up is to track the checkpoint log, so I can lose the hilariously
long sleep...
Configure checkpoints and changelog
More normal naming for package object
Rename test and make more general

Now it inspects config to see all the topics it should tail.

This is pretty good now; I should be able to add more tests without
messing with it too much.
WIP: exactly-once stream offset tracking

Only pure transformations work right now, but it's a start!

This relies on a patch to Samza that allows the flush of a single input
stream. This is necessary to ensure the downstream output will be
persisted before we save the offset pair.
WIP: exactly-once aggregations

Plus the usual thrashing.
Exactly once merges

This adds a coast-specific Kafka-backed system as well, which is
responsible for ensuring that messages are sent in the right order.

The merge implementation is rather heavyweight, since it involves
writing all the data twice. (It turns out to be hard to do the
lightweight version with the existing interfaces.) This should be enough
for a proof of concept, but it will need to be revisited later.
Labelled merge branches

I've been meaning to do this for a while. This makes it easier to
generate meaningful paths in the AST, which should be easier to debug
and more resistant to refactoring.
Improvements to the dotfile compiler

Prettier output with more information.
Yank examples out of ExampleSpec

Mostly I wanted to print the dotfile for this, but I also took the
chance to document it a bit.
Work across many partitions in parallel

Mostly just picking a partition key and getting that out.

I think I'd rather *not* use the array hash as the partition key; seems
to deserve its own typeclass. We'll see...
Merge branch 'samza-lite'

This has been a long time out of master, and includes some
general-purpose improvements.

Samza code's still not quite ready yet (groupings are not exactly-once,
plus some cleanup) -- but it's still an improvement on the existing
version.