add Kefir.fromEvent(target, eventName, [transformer])
emitter methods should return `this` for chaining
rename `pool` methods to plug / unplug
docs
docs
0.2.7
Merge branch 'master' into gh-pages

* master:
  0.2.7
  docs
  docs
  rename `pool` methods to plug / unplug
  emitter methods should return `this` for chaining
  add Kefir.fromEvent(target, eventName, [transformer])