reST parser refactoring

Testability improved. No change in behaviour.
Added --test-patch version to verify if the script is working
Make sure we die if `--test-patch` fails.
Added options to customize known directives output
Better rendering of Sphinx directives

List of domain directives still incomplete.
Props to @dvarrazzo.
Return UTF-8 encoded HTML from Rest.
Find Python, use it to execute rst2html, make sure we have docutils.
Use $encoding to specify reST intput encoding.
Note encoding fixes.
Update comment.
Use HTML output for Sphinx math stuff.
Always return UTF-8.
Timestamp v0.16.
Increment to v0.17.
Add Asciidoc support.
Timestamp v0.17.
Increment to v0.18.
Require HTML::Tagset for Text::MediawikiFormat.

Since it only recommends it (WHU?). See http://www.cpantesters.org/cpan/report/b45f2e54-648b-11e1-9403-17152a34c07f for reference.
Exclude all Pod tests from the distribution.