Display power-assert output in mini reporter

[vadimdemedes]

This PR fixes #372.

Mini reporter (default one) was not displaying power-assert output. Now it does (along with a stack trace):

[sindresorhus]

LGTM

// @ben-eb

[ben-eb]

👍

[jamestalmage]

LGTM.

Though I think this highlights some deficiencies in our API.

Instead of separate errors and tests arrays, should it just be tests? A test could have a status attached (passed / failed), and all assertions with their respective results. Might be better than just standardizing errors as described in #365

[sindresorhus]

Instead of separate errors and tests arrays, should it just be tests? A test could have a status attached (passed / failed), and all assertions with their respective results. Might be better than just standardizing errors as described in #365

👍 Can you open an issue?

[vadimdemedes]

@jamestalmage we also need to store rejections and exceptions, which are not attached to any test and don't have test title, etc. So storing rejections and exceptions in tests doesn't sound right.