Capitalization

[trvrb]

Currently this is the only build that is capitalized. I think it's strange to simultaneously have https://nextstrain.org/tb and https://nextstrain.org/WNV. Especially because https://nextstrain.org/wnv errors out with a 404. Having auspice care about capitalization is just fine. But I would propose to change the augur outputs here to wnv_na_tree.json, etc... for consistency.