Add asyncsignalstream and multisignal. 

run_task() is now a function instead of a method. 

Achieve 100% code coverage. 

asyncslot() now keeps weak reference to methods. 

asyncslot now returns Task object. 

Last version with nested task enabled by default. 

Add modal support. 

Add QiLoopMode enum. 

Version 0.5.0. 

Update README.