mkdir before compile-json
Some minor refactoring
Fix link on 404 page.

TODO this 404 text should be internationalised.
Merge pull request #389 from g0v/i18n-cleanup

Improve i18n workflow
[#389] Don’t warn if i18n/ exists.
[#389] Clarify translation instruction a tiny bit
Merge remote-tracking branch 'origin/master' into tw-l10n