Topic/rww updates

a couple of bugs I found while integrating banana with [rww-play](https://github.com/read-write-web/rww-play)
I admit: I am getting lost in the new dependencies :-/

Can you quickly explain why moving those dependencies from `plantain_common_jvm` to `plantain_jvm` was the right thing to do?

Otherwise, no specific issue with the PR, I'll merge right after the tests pass, and your answer here :-)