Show sets in output

[EvanHahn]

Before this change, Sets were not shown in the output.

For example, t.alike(new Set([1, 2]), new Set([3, 4])) would show:

not ok 1 - should deep equal
  ---
  actual:
  expected:
  ...

Now it shows this:

not ok 1 - should deep equal
  ---
  actual:
    - 1
    - 2
  expected:
    - 3
    - 4
  ...

[mafintosh]

Awesome! 3.4.1