* Cleanup mentions about glide
* Don't use glide to ignore vendor directory
Since go-1.9, "./..." no longer contains the "vendor" directory.
Also, since #1305 migrated dependency management from glide to go mod,
there is no need to think about the "vendor" directory.
See: https://golang.org/doc/go1.9#vendor-dotdotdot
* go mod tidy