Update TAP reporter to TAP 13

[lencioni]

I noticed that mocha is using the older TAP specification and wondering if you would be open to updating it to TAP 13? It is pretty similar. I think the main differences are that version 13 starts with a line that says TAP version 13, and encodes test output in YAML.

General format:

TAP version 13
1..N
ok 1 Description # Directive
# Diagnostic
  ---
  message: 'Failure message'
  severity: fail
  data:
    got:
      - 1
      - 3
      - 2
    expect:
      - 1
      - 2
      - 3
  ...
ok 47 Description
ok 48 Description
more tests....

[cades]

+1 for TAP 13
with YAML, multiline error message can be handled correctly by testem test runner.