An issue was reported (see #1721) where, in docker containers where the
`LANG` was not being set, `Precious::App` would serve Mustache templates
in an ASCII encoding. This caused templates to error out.
In the past, this would have happened in environments where `LANG` was
not set and the Gollum applciation configuration had enabled MathJax.
Now, it happens even if MathJax is disabled because of a UTF-8 character
I added to the mobile navigation menu.
Basically, we should enforce a UTF-8 encoding from now on to avoid
runtime errors related to ASCII encoding.
benjamin wil
2b12ab9206