Rewrite binder stream factory to compose all others

* `asStream` - rename `fromBinder`
* `fromBinder` - asynchronously unbind synchronous binds to keep signature clean
* `asEventStream` - fix not using `eventTransformer`
* `fromPoll` - no longer require events except `End`
* `fromEventTarget` - support MVC observer convention
* `partiallyApplied` - accept variable argument lists
* format - parenthesesize single line invocations
* complexity - reduce implementation 30 lines!
* `README` - needs updated correspondingly