bug: break the loop for writing data to peer when there is an error

Fixes panjf2000#368

chore: fix some wrong comments

chore: refine eventloop.read(*conn)

chore: update READMEs

Breaking API changes and optimizations

opt: put the static buffer back to pool to reduce more memory usages

chore: update some comments

chore: resolve the lint issue of staticcheck

bug: set the status of ring-buffer to non-empty after it grows its size

Fixes panjf2000#288

opt: improve the management logic of the mixed-buffer