Change README header to url community.rxswift.org
Change README header to url community.rxswift.org

Also add branch specification for PR's

thanegill/rxswiftcommunity.github.io,RxSwiftCommunity/rxswiftcommunity.github.io,RxSwiftCommunity/rxswiftcommunity.github.io,RxSwiftCommunity/rxswiftcommunity.github.io,thanegill/rxswiftcommunity.github.io