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.
- some small bugs are now fixed
- include comments in error messages (if this causes issues, use --hide-comments)
- colors should make more sense now
- error-related things moved to mers_lib/src/errors/