Fix bug 924347: Fx download button default to en-US.

Previously for release Fx it would search for the build
in the locale that had the largest version number that
wasn't a pre-release or ESR. For some locales this was
returning a very old release. This alters this to only
return the latest release, and thus causes the button
to always give the latest release by defaulting to en-US
if no localized build is available.
Merge pull request #1384 from pmclanahan/fix-download-button-version-checking-924347

Fix bug 924347: Fx download button default to en-US.
Bug 768435 - Link Mozilla Firefox logo on new [Bedrock] Firefox pages
Bug 933936 - Vans Triple Crown home page promo

Now with mixins and multilingual links!
Merge pull request #1391 from mozilla/bug-933936-vans-triple-crown-home-promo

Bug 933936 - Vans Triple Crown home page promo
Merge pull request #1389 from kyoshino/bug-768435-logo-links

Bug 768435 - Link Mozilla Firefox logo on new [Bedrock] Firefox pages