use System.Predicate<T> rather than defining Filter<T>
rename IProducerThreadSubscriber to IProducerThreadReceiver
rename ISubscribable to IReceiver
rename BaseSubscription to BaseReceiver
update README.md
BaseReceiver: simplify
rename ChannelSubscription to Receiver
factor IFiber reference into BaseReceiver
rename LastSubscriber to LastReceiver
rename BatchSubscriber to BatchReceiver
renamed KeyedBatchSubscriber to KeyedBatchReceiver
(I)Channel: rename paramters from subscriber to receiver
remove SubscribeTo*() methods from Channel, IChannel, define them as extension methods in the cs file of their respective receiver implementation
combine IReceiver and IProducerThreadReceiver interfaces, simplify method names
remove incorrect comment