misc/completion/ipfs-completion.bash: add `ipfs stats` to BASH completion

core/commands/mount_unix.go: ensure error is not nil before printing it

contribute.md: fix bibliography indexing in example

core/commands/swarm.go: change tabs to spaces in USAGE message

*: 80-column readability improvements

License: MIT
Signed-off-by: Thomas Gardner <tmg@fastmail.com>