Navigation breakpoints don't "fit" for Greek and Russian

[emersonthis]

Bug:
The breakpoint that determines when the navigation gets hidden behind the hamburger works for English and the romance languages. But the words are longer for Greek and Russian, so there's an awkward overlap on "in between" size screens (tablets, etc)

Suggested fix:
The easy (read: lazy) solution would be to just set this $on-tablet breakpoint higher. But this will effect a lot of other styles, so I don't recommend it.

A better solution would be to coordinate with translators to maybe choose shorter words for the nav, if there are acceptable synonyms.

It would also be ideal for the nav to be implemented in a way that's more resilient, and fails more gracefully. The overlapping is the result of absolute positioning, which tends to be problematic and hard to maintain. Maybe we could redo it using flexbox or a different strategy that perhaps results in text wrapping when it doesn't fit (instead of overlapping in an unusable way).