Update i18n plugin

.gitignore

pelican-plugins/i18n_subsites/README.rst

pelican-plugins/i18n_subsites/i18n_subsites.py

...n-plugins/i18n_subsites/implementing_language_buttons.rst

pelican-plugins/i18n_subsites/localizing_using_jinja2.rst

...8n_subsites/test_data/output/an-untranslated-article.html

...sites/test_data/output/cz/an-untranslated-article-en.html

...gins/i18n_subsites/test_data/output/cz/feeds_all.atom.xml

pelican-plugins/i18n_subsites/test_data/output/cz/index.html

...-plugins/i18n_subsites/test_data/output/cz/pages/404.html

...i18n_subsites/test_data/output/cz/translated-article.html

...est_data/output/de/drafts/an-untranslated-article-en.html

...gins/i18n_subsites/test_data/output/de/feeds_all.atom.xml

pelican-plugins/i18n_subsites/test_data/output/de/index.html

...-plugins/i18n_subsites/test_data/output/de/pages/404.html

...sites/test_data/output/de/pages/untranslated-page-en.html

...i18n_subsites/test_data/output/de/translated-article.html

...plugins/i18n_subsites/test_data/output/feeds_all.atom.xml

pelican-plugins/i18n_subsites/test_data/output/index.html

...can-plugins/i18n_subsites/test_data/output/pages/404.html