Fixes #288 (Upgrade to rxjava 1.0.1)
Fixes #287 (Flush HTTP response on completion of `RequestHandler.handle()`)

Introduced a method flushOnlyOnChannelReadComplete() in HttpServerResponse to optimize for "hello world" usecase.
Otherwise, the response is always flushed after the `Observable` returned from `RequestHandler.handle()` terminates.
Fixes #277 (StackOverflow while draining`UnicastContentSubject`)

Short-circuiting if PassThruObserver is already draining the notifications.
Merge pull request #289 from NiteshKant/0.x

Fixes #288 #287 #277