CLI doesn't support ansi terminals with 3-bit colors

[daviddavis]

A user on the pulp channel ran into a problem where their text was blinking. The command tput colors showed that their terminal only support 8 colors.

We're using a 256 color formatter (see here). I think we need to make the CLI smarter and have it fall back to use the colors the terminal provides or automatically disable color support if the terminal doesn't have 256 colors.

A quick scan of httpie looks like maybe it handles this: https://github.com/httpie/httpie/blob/464b5b4c1d8b3e72255739094e17a013d80abae7/httpie/output/formatters/colors.py#L57-L66