Allow outputting color with `--output` with `--color=always`

[Qyriad]

This allows forcing color output even when outputting to a file, with --color=always. -o /some/file with the default --color=auto will still default to no color.

This makes it easy to separate the colorful strace output from the output of another program that is writing to stderr. It's also handy for showing strace's color output on another terminal from the command being run.