move allocation of to-delete into players-view

since serra-view doesn't actually do anything with it
connect commander damage plumbing

somewhat iffy on some of this but it's not too bad

mostly I don't like having to pass that commander-damage channel down
through player-view. i also feel somewhat weird about the fact that
there isn't one cannonical place where a player's life is
modified. arguably this should be done by commander-damages-view passing
something down a channel rather than just transct!ing directly but w/e
add title to serra-view
fix state bug when deleting a player

make sure to clean up damages in addition to removing them from the
players list
prevent duplicate players

disabling the buttom isn't enough, since they can still be added with
enter
see ess ess
"no players" message when there arent any
dont render commange damage when we dont need to

apparently empty collections aren't falsy in clojure (yay!)
styles, styles
prevent blank string players from being added
add css reset