Enable a default test suite or suites in the configuration file

[chadharrington]

By default, running bin/kaocha runs all test suites. This is undesirable when some test suites are expensive or require specific environments, etc. It would be great to be able to configure which test suite or suites should run as the default when no test suite name is passed.

Leiningen does this via the :test-selectors key in project.clj.

[plexus]

Leiningen test selectors aren't quite the same thing, as lein-test doesn't have the concept of test suites, but nevertheless I agree this could be useful.

A simple :kaocha/default-suites key which defaults to the ids of all test suites would do the trick.

[plexus]

The plan is to solve this via test selections, see #364