- Added `TestAgent` helper class.

  This class provides simple to use helpers for running your tests with the agent
  and in transactions.

- Added `tap` assertions.

  If your tests use [`tap`](https://www.npmjs.com/package/tap), then you can add
  some helpful assertions to your tests using this module.

- Added version matrix test running.

  This is a script for executing your instrumentation's tests against many
  versions of the module you are instrumenting.