This implementation of multilanguage Sitemap brings to CMSSitemap all the (published) language entries in the same sitemap.
This is achieved by using Title as the base item for the sitemap.
Do we need to have language-specific sitemaps too?
I had to use .date() in tests because of subtle time skewes in Travis
Multilingual sitemap. Base objects switched to Title.
Test for multilingual sitemap. Switch to date-based checks for lastmo…
…d to avoid timing skew issues.