[Bug 1033339] Fix error in download warning.

The max version of the version if a `<` version, so it is the next version number. The min version is the right number to use.
Serve Yaocho localization files.

This lets Yaocho re-use the machinery from Kitsune that generates the
client-side javascript localization files from .po files.
[bug 1038724] GA events for download button