An indeterminate workflow in which one task merges and "shuffles" output
streams from several tasks.
emitSignals now can accept an array of signal instances and emit them as
separate signals.
New implementation of invokeTaskFunction (invokeTaskFunction2) which no
longer dereferences signal values but gets them as additional argument.
Also, the function now deals with multiple instances of a given signal
received at once.
Continuous tasks "cchoice" and "cdataflow" now use the fetchInputs API.
They are now capable of correctly dealing with multiple input signals
awaiting in the queues (which is demonstrated on the Twitter Map/Reduce
workflow).