fix up docs
remove request body of set request in slowlog

Some request could includes invalid UTF-8 sequence.
v0.8.6 released
fix up style
logging error to apply configuration
fix bug(single graceful restart sometimes fails)

As blocking master-process by waitpid after receving SIGCONT,
master-process sometimes receives SIGCHLD.

As SIGCHLD is used by master-process for restarting
crashed worker-processe, don't recevie SIGCHLD in the situations except it
v0.8.7 released