pass termCh to mainloop for loop controll
wait up to 30 seconds for terminating until `postQueue` is empty
add test for terminating
remove unnecessary loop
change broadcast terminating timing
output error message when the post values are abandoned
add comments
add comment
remove `exitCh <-` in main loop, use direct return
s/loopStateTerminated/loopStateTerminating/
define NewPostValue for struct initializer
use defer Luke
fix nit changes
Merge pull request #42 from mackerelio/feature/graceful-quit

Feature/graceful quit