check for a translation link instead of a specific markup
+ tests on translations
Transformed expected URL pattern into a constant regex at the top of the rule.

Being a bit more flexible with that pattern now; eg HTTPS is fine, case insensitive.

Formatting URL in warning using <code>.
Merge pull request #61 from w3c/denis/translation-checker-fix

Tests pass, checks seem OK. (I've made a few small changes, though &mdash; see my commit.)