trifle: refine ReadBufferCap option and add comments

doc: update the description about ring-buffer

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