Add ability to use compact version of sequence of mappings

[rypervenche]

Would it be possible to add an adverb or some way of getting the compact version of a sequence of mappings? I find that this formatting is much more common.

---
sequence:
-
  a: b
  c: d
---
# compact
sequence:
- a: b
  c: d

Thanks!

[Leont]

I'm guessing you're talking about the YAML outputting code? Patches welcome?