trifle: add comments for exported functions

opt: keep running when an error occurs in connection

Fixes panjf2000#142

feat: support locking each I/O event-loop goroutine to an OS thread

Fixes panjf2000#133

trifle: add comments

opt: improve the conversion between string and byte slice

opt: refactor the load-balancing algorithm of source addr hash

test: fix a few issues in TestLengthFieldBasedFrameCodecZeroPlayLoad

Updates panjf2000#113

trifle: rename functions and refine comments

fix: resolve the issue of closing one fd twice

opt: Leverage system calls instead of `net` package to create listeners

Also enable SO_REUSEPORT to avoid Thundering Herd, besides, Fixes panjf2000#47 panjf2000#44 panjf2000#77