Various small improvements/fixes

[chaoflow]

No description provided.

[tomerfiliba]

@chaoflow - about the ANSI colors change, be sure to add if sys.stdout.isatty(), and do it only on posix-systems (e.g., not windows)

[chaoflow]

pushed

[tomerfiliba]

thanks. that got me thinking that a colors would be useful in general. i'll add something more general to plumbum.cli.terminal.

[chaoflow]

@tomerfiliba, @coroa: I'm currently investigating https://github.com/mitsuhiko/click as an alternative for cli parsing for https://github.com/chaoflow/tpv.cli. You might want to take a look before implementing more generic colour support - plumbum.cli could be based/replaced by click.

[henryiii]

By the way, colored is a nice library for colors in Python. I would love to have something built in, though, especially with context manager support, like I use here.