Fixed grant commands.

The 'on' and 'to' should not be capitalized.
Fixed badarg when a user is disallowed.

The return from the error is a binary when disallowed, so trying to do
list_to_binary/1 on it is a problem.
Merge remote-tracking branch 'origin/develop' into bug/mw/security-fixes
Merge pull request #362 from basho/bug/mw/security-fixes

Fixes calls into security

Reviewed-by: rzezeski