Implement Queue so Toast do not overlap

[8bitAlex]

Currently doing multiple Toast.show(...) will make them overlap each other. There should be a queue that manages how they are shown on the screen so as one fades out the next one can fade in without conflict.

[geminiyellow]

+1

[BenjiFarquhar]

+1

[bluekurk]

@8bitAlex it has "onHidden" callback so make a array as queue with pop()/unshift() seems not that hard...

[gaurav341]

I have created an example for handling multiple toasts using the message queue. Gist link