0.3.17

• Use FuturesOrdered in join_all (#2412)
• Add {future, stream}::poll_immediate (#2452)
• Add stream_select! macro (#2262)
• Implement Default for OptionFuture (#2471)
• Add Peekable::{peek_mut, poll_peek_mut} (#2488)
• Add BufReader::seek_relative (#2489)