Make separate steps default behaviour

[albertjan]

Coming back to this after a few months the default behaviour for the mocha test runner to do all the steps in one test seems a bit awkward. I suggest we make separateSteps: true the default behaviour.

@adamjmcgrath what do you think.

[adamjmcgrath]

TBH am thinking of reverting back to separateSteps: false on our app, because tests timing out while your debugging steps can be a nuisance. eg.

Step A
Step B // Paused on breakpoint for > 5 secs (mocha timeout)
Step C // test times out and fails before this step is run

Rather than:

Step A, Step B, Step C // spend as long as you like on a breakpoint on Step B, you can still jump into Step C without the test stopping.

This might be a poorly configured mocha thing though, separateSteps: true does look nicer 😄