return true if actually closed, flase for already closed
more explict close status; clean code
make as close even if no close handler; close handler does not need to wait all message handled
clean code
{:body body} is also accepted. experimental global send/receive
faster code than String.getBytes("ISO-8859-1") when encoding http header key
Remove vestigial dependency: org.clojure/tools.macro
Add `run-server` reference to migration guide