only transformed configs/with_string so far,
but other configs/* should follow soon.
also, this will help with implementing
new stdlib functions in the future.
this also includes support for the NoTheme,
a theme which doesn't add any color to mers'
output.
If you compile mers with --no-default-features,
the `colored` dependency will disappear and
mers_lib will fall back to NoTheme.