ls style --color option

I missed the colored usernames when doing things like this:

    t timeline | less -R

so I changed the `--no-color` option to `--color=COLOR` in the style of the `ls` command where `COLOR` can be:

`auto`: only output color when stdout is a tty (default)
`always`: always output color
`never`: never output color

Not sure if it's worth merging into the main repo or not, but I thought I'd give it a shot.