Add a global --color=auto/never/always flag

At the moment, it is only zappa tail that supports a --no-color and a --force-color argument.

I'd like to suggest instead making a global --color=[auto|never|always] flag, which would affect all subcommands. There is currently no way to force color on zappa status which is why I'm filing the issue.

That particular --color= flag syntax is very standard across all unix tools (grep, ls, etc)