v4.0.0

New features:

• multicall
• batch
• listNotifications
• listMethods
• class Aria2 is an EventEmitter

Breaking changes:

• removed callback interface
• removed browser bundle
• onopen, onclose are now events open and close
• onmessage is now event input
• onsend is now event output
• send method has been replaced with call
• requires Node.js >= 7.6.0

Minor changes:

• example removed
• browser tests removed
• use ava for testing