• Transducers via Observable.transduce()
• adapt_call no longer requires the inspect module
• Support callable instance, instance method, and class method for adapt_call
  thanks to @succhiello.
• Added example using concurrent futures for compute-intensive task
  parallelization, thanks to @38elements.
• Got chess example working again under Python 2.7 thansks to @enobayram.
• Added example for async generator.
• Many PEP 8 fixes.