[add] Use throttleFirst operator

[add] Refactor HttpAsyncConnection of Sprout

[add] throttleLast

[add] meeting

[add] flatmap

[add] empty, flatmap

[add] map

[add] error

[add] timer

[add] interval

[add] range

[add] fromArray

[add] Just

[add] Constructor without arguments

[add] Debug subscriber

[add] Observable

[add] Thread util

[fix] Running thread

[add] Flowable using Reactive Streams

[add] Application class

[add] MainActivity of java and kotlin

[add] Project