Elia Camposilvan

Results 2 issues of Elia Camposilvan

Related to #75. This PR aims at adding a **makeReplaySubject** source. Please note that replay subjects should replay values even after completion

This should act as a subject, with the addition of emitting **immediately** old values to new subscribers, in FIFO order. The api could look like: ```reason let makeReplaySubject: (bufferSize: int)...