Fix stderr color dependence on stdout

[spoutn1k]

Hello,

I work with programs that pipe stdout often. simple_logger would simply not print colored output to stderr when that happened. This is due to this colored issue.

This PR aims to fix this by implementing a variation of the set_up_color_terminal function, enabled when the stderr feature is selected on other platforms than Windows (For lack of testing environment).

[spoutn1k]

I renamed the references to the coloring feature from colored to colors as is defined here:

rust-simple_logger/Cargo.toml

Lines 10 to 12 in f12a2b3

	[features]
	default = ["colors", "timestamps"]
	colors = ["colored"]

That may be a mistake please let me know if I should roll that back.

[borntyping]

Thanks! I think this will fix #71 too.

I renamed the references to the coloring feature from colored to colors as is defined here

I think this change makes sense, I'm not really sure why it was written that way, since coloured is a dependency not a feature.

There's some documentation around set_up_color_terminal in the README that will need updating. (I'll do it when I merge and release this—hopefully later today or this week—if you don't get there first!)

[borntyping]

Released in 5.0.0.

• https://crates.io/crates/simple_logger/5.0.0
• https://github.com/borntyping/rust-simple_logger/releases/tag/v5.0.0