Should add multi lang into Fling tutorial as the attachment

[Blocking Requested - why for this release]:

Comment on attachment 8737169 [details] PR #15 @Rex, This patch adds multi lang files, thanks

The patch itself seems good to me, but I'm not sure if this is the proper flow to add multilanguage support on an external site for us.

I think it should be better to describe 1. where did you get the l10n strings 2. how do we maintain the translation with community and l10n team after committing it. Should we really responsible for committing l10n string changes and reviewing **every time** there's a translation change? I don't thinks this is a proper flow for engineering work.

And I'm also not a proper one to confirm if there are translation problems. So if the translation is surely processed and reviewed on somewhere (like a bug), please put them here rather then just open a bug and say nothing but a reviewing request.

These translations are for the send-to-tv website. The translations are done by partner however we have to put the translations on the website by ourselves currently since this website is maintained by us and unlike apps, partner cannot access the website to integrate the translations.

Land to Master: https://github.com/mozilla-b2g/casting-tutorial/commit/b63b4bedc9fc39dcd993298d61b11867e8b239c7

The server is updated in the bug 1262722