eventlisteners works if a listener is removed
eventlisteners works if a listener is removed

In the current version, a event-listener is never removed, which leads to problems in certain use cases. This patch fixes this.
paldepind/snabbdom,staltz/snabbdom,snabbdom/snabbdom,snabbdom/snabbdom,paldepind/snabbdom,snabbdom/snabbdom,snabbdom/snabbdom,staltz/snabbdom,staltz/snabbdom