Merge pull request #34 from mozillazg/master

Add Simplified Chinese translation
French l10n.
Merge pull request #38 from BertrandBordage/master

French l10n.
Allow for i18n testing.
Add Spanish translation.
Update PO files.
Update documentation.
Improve documentation cross references.
Requirements unification.

--HG--
rename : tests/test-requires.pip => tests/requirements.pip
Remove old Python3 requirements file.
Integration tests: fix teardown calls order.
Add versioned test requirements.
Update documentation in preparation for release.
Added tag v2.0 for changeset 8577fee7b502
Merge pull request #1 from frankban/master

sync with main repo