Don't allow wp-cli as root without --allow_root
Rename --allow_root to --allow-root
Adjust spec for --allow-root

I know file=false is the default, but were that to change at any point,
having this be true could potentially compromise the system's security
if wp-cli was run as root.
Don't show --allow-root in help.

It'll still be there, it just won't show up in the man pages anymore,
since the "NOT RECCOMENDED" is pretty ugly. :)
Minor typo fix.
Recommend sudo instead of su.
Merge pull request #973 from SpikesDivZero/no-root

Don't allow wp-cli as root without --allow_root