Fix email matching

The regular expression used to match too much characters: to match a dash, “-”
must be the first or the last character of a character set (“[…]”), otherwise
it indicates a character range.
Fix the counting of articles in groups

This was a stupid arithmetic mistake: there is (last - first + 1) articles in a
group, not just (last - first)…
Stop any open tag at the last line of articles
Merge pull request #2 from pmderodat/master

Tiny fixes for previous branch features