test cases of merging std(out/err)
feature: merge std(out && err)
a new option `-l, --log` for merging std(err && out)
docs of Advantage Logs (merge stdout && stderr)
fix a small bug on unix
print messages
fix: when `reload/restart` is called, listeners of stdio should be removed.
Revert "fix: when `reload/restart` is called, listeners of stdio should be removed."

This reverts commit b94b659a1323eb7321642893f4f24f3bdbbb3301.
fix: when `reload/restart` is called, disconnect the previous at first.
Revert "fix: when `reload/restart` is called, disconnect the previous at first."

This reverts commit 7c27ff9331b905e63cd33b7f47158514e82fa38d.
fix: when `reload/restart` is called, disconnect the previous at first.
make sure stdio exist and graceful exit when `reload/restart`
Merge pull request #822 from Tjatse/master

feature: merge std(err && out) logs and tidy logic of stdio