Make test output clearer in verbose mode. #91

Discussion under 5d8820b introduced verbose config option which shows test's duration and timestamp.

Since this mode (by definition) contains a lot of data I think it would be useful to make the output as readable as possible.

1. Skip duration for tests where duration is 0 to reduce clutter (test_2 in the example).
2. Use some form of highlighting to differentiate between significant digits and leading zeros. That way it will be easy to visually assess the order of magnitude of the individual duration.