nitpretty: Introduce nitpretty, a Nit pretty printer.

Signed-off-by: Alexandre Terrasa <alexandre@moz-code.org>
tests: add tests for nitpretty

Signed-off-by: Alexandre Terrasa <alexandre@moz-code.org>
lib: format standard using nitpretty

Signed-off-by: Alexandre Terrasa <alexandre@moz-code.org>
gitignore: add .nitpretty to ignore list.

Signed-off-by: Alexandre Terrasa <alexandre@moz-code.org>