Assorted minor things to polish off #28.

- Join connection header tests back together again
  (now that they're working again).

- Add/improve some code documentation.

- Some slight style cleanup.

- Add the `test_from_stream_asctime_double_digit_day` test
  (its doc comment explains its *raison d'être*)
Add a `consume_lws` method (it'll be wanted soon).

This augments `consume_optional_lws`.

For the ignorant, the original is:

	A thousand hairy savages,
		Sitting down to lunch:
	Gobble, gobble, glup, glup,
		Munch, munch, munch.
Switch from old-style fail! to new-style.
(I'll leave it named fail2! until next snapshot).
Switch info!, debug!, fail! to new format.