[assets] Explicit requires instead of require_tree
[assets] Explicit requires instead of require_tree

It's better for keeping track of dependencies and complexity, and for
preventing dead code.

apardo/nolotiro.org,apardo/nolotiro.org,apardo/nolotiro.org,alabs/nolotiro.org,alabs/nolotiro.org,alabs/nolotiro.org,apardo/nolotiro.org,alabs/nolotiro.org