Color test run times

Test run times should be colored as follows:

- Semi-slow tests in yellow. Take this as a warning to improve them, but shouldn't stop you from committing
- Slow tests in red. You should probably fix those asap, unless you wanna have the slowest suite on the earth

After some measurements in a big production app, our tests are on average `0.001s`, and there are just a few slower ones.
Since objc is really fast with tests, I've set these boundaries:
- 0.00s - 0.025s fast test
- 0.25s - 0.100s slowish test
- more than 0.1s - slow test