New policy regarding pullrequests on GitHub

[BlackDaemon]

Just now, i had a discussion with main rpcs3 devs (DH, Nekotekina, Oil) about some corrections to merging pull requests into master branch. We came to agreement, that it's better to merge major changes, which slightly unfinished/unstable, than keep it for polishing for months. For now master branch will become some sort of nightly branch, which could contain unfinished/unstable code. Stable build will be prepared in case of new release. We hope, that this could help us to bring more good and cool changes, despite minor hiccups there