Add 'nocolor' option for output.

This maintains most output styles, but removes coloring from output. On Windows,
this is the default setting if Full would have been used

src/main.rs

@@ -115,11 +115,12 @@ fn main() {
                 .short("s")
                 .takes_value(true)
                 .value_name("TYPE")
-                .possible_values(&["auto", "basic", "full"])
+                .possible_values(&["auto", "basic", "full", "nocolor"])
                 .help(
                     "Set output style type (default: auto). Set this to 'basic' to disable output \
                      coloring and interactive elements. Set it to 'full' to enable all effects \
-                     even if no interactive terminal was detected.",
+                     even if no interactive terminal was detected. Setting to 'nocolor' maintains \
+                     all advanced output, but uses no colorization.",
                 ),
         )
         .arg(
@@ -149,6 +150,7 @@ fn main() {
     options.output_style = match matches.value_of("style") {
         Some("full") => OutputStyleOption::Full,
         Some("basic") => OutputStyleOption::Basic,
+        Some("nocolor") => OutputStyleOption::NoColor,
         _ => if atty::is(Stream::Stdout) {
             OutputStyleOption::Full
         } else {
@@ -156,7 +158,14 @@ fn main() {
         },
     };
 
-    if options.output_style == OutputStyleOption::Basic {
+    // We default Windows to NoColor if full or auto had been specified.
+    if cfg!(windows) && options.output_style == OutputStyleOption::Full {
+        options.output_style = OutputStyleOption::NoColor;
+    }
+
+    if options.output_style == OutputStyleOption::Basic
+        || options.output_style == OutputStyleOption::NoColor
+    {
         colored::control::set_override(false);
     }