The road to simpler message bus

[yamalight]

To simplify the lib, create a plugin for method aliases and move them out from core, making them optional.

• [x] Create plugin for Bus-level aliases: observe, subscribe, onNext
• [x] Create plugin for Channel-level aliases: subscribe/subscribeTo, onNext/onNextTo, request(topic, opts)
• [x] Publish aliases plugin on github and npm
• [x] Simplify core methods syntax
• [x] Allow changing used Subject type during it's creation (#4)