Automated test suite

[ept]

Somewhat embarrassingly, Bottled Water currently does not have any automated tests. I've only been testing it manually, which is obviously not good for the long term.

I've been hesitating on tests so far because it's not clear how to best test something like Bottled Water. Ideas include:

• PGXS contains a simple test framework for Postgres extensions. This works by running a SQL script against a database, and the output is compared to expected output. Bottled Water's SQL functions could be tested this way, but the logical decoding output plugin can't.
• There are some generic test frameworks for shell scripts, such as Bats or assert.sh. To get reasonable test coverage we'd probably need to do integration tests (including bringing up Postgres, ZK, Kafka and schema registry, and testing network issues between them) so we'd need to figure out how to do that within a test framework.
• If we have JNI bindings (Give consumers access to transaction structure #2), we could use a more expressive JVM-based language for writing the tests, which would probably be a lot more pleasant than writing tests in C or Bash.