colorstring doesn't obey $TERM settings and doesn't support non-vt100 tty

[korfuri]

Hi, thanks for this lib, it's very convenient. One small issue I have with this is that this makes coloring unconditionally assume that the output of the program is a vt100 tty. The termcaps it emits aren't compatible with other terminals. While vt100-compatible basically won the war of terminals, it's not the only standard out there. This also makes it impossible to disable color output by tweaking the TERM environment variable.

It would be good to load escape sequences from the termcaps db based on $TERM instead of hardcoding them.

Thanks!