This will avoid some copy/paste in future tests.
The commit also fixes a typo and a missing --DOC_NO_DASH which breaks
rendering with one of the markdown implementation.
This adds require("_date") to some example tests that use the current
date via os.date. This allows reproducibility by replacing os.date()
with a function that uses a static date from $SOURCE_DATE_EPOCH. See
commit 9d7eaf0 for more details.
Signed-off-by: Uli Schlachter <psychon@znc.in>