Don't use termion for dua aggregate coloring on windows

[Byron]

This is already sufficiently abstracted…

dua-cli/src/common.rs

Lines 117 to 145 in b7ed2bb

	pub enum Color {
	/// Use no color
	None,
	/// Use terminal colors
	Terminal,
	}
	pub(crate) struct DisplayColor<C> {
	kind: Color,
	color: C,
	}
	impl Color {
	pub(crate) fn display<C>(self, color: C) -> DisplayColor<C> {
	DisplayColor { kind: self, color }
	}
	}
	impl<C> fmt::Display for DisplayColor<C>
	where
	C: fmt::Display,
	{
	fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
	match self.kind {
	Color::None => Ok(()),
	Color::Terminal => self.color.fmt(f),
	}
	}
	}

…which should make it straightforward to use a 'color-crate' that is cross-platform. Maybe it's possible to use that on linux as well, but it's not mandatory as it would also increase compile times.

Related to #2