fix ~ avoid panic if running on early windows without ANSI escape con…

…sole support

.# Discussion

Versions of Windows prior to one of the v1511 Windows 10 builds (likely
10.0.10586.589; released on 2016-09-13) do not have built-in console
interpretation of ANSI escapes. After Win10 v1511, ANSI escape interpretation
is available, when enabled via `SetConsoleMode()` (see [4]). Earlier versions
(back through Windows 7 to XP) *do* have 8-bit color available via the Console
API, but it's more cumbersome to access (especially from the `rust` realm)[5].

Pre-ANSI escape color may be too cumbersome to use, but the majority of
`pastel` has usefulness even if not displayed in color. "colorcheck" and "pick"
are obvious sub-commands which are unusable without some color support and so
both are disabled with an error message. "format" and "list" are modified to
only display non-colorized output. "paint", a judgement call about error vs
un-colorized, is left operational but without colorized output.

[1] [MS ~ Release Blog Post](https://devblogs.microsoft.com/commandline/24-bit-color-in-the-windows-console) @@ <https://archive.is/6UTBA>
[2] [Reddit ~ Win 10 ANSI Escapes](https://www.reddit.com/r/Windows10/comments/44czox/windows_10_v1511_adds_support_for_ansi_escape) @@ <https://archive.is/7l6tz>
[3] [MS TechNet Win 10 Versions](https://docs.microsoft.com/en-us/windows/release-information/) @@ <https://archive.is/sv3LN>
[4] [`ansi-term` ~ enable ANSI](https://github.com/rivy/rust.ansi-term/blob/ff7eba98d55ad609c7fcc8c7bb0859b37c7545cc/src/windows.rs#L25-L57)
[5] [rust-users ~ Windows color](https://users.rust-lang.org/t/colored-terminal-output/24604/12) @@ <https://web.archive.org/web/20190905231230/https://users.rust-lang.org/t/colored-terminal-output/24604/12>

Cargo.toml

@@ -28,6 +28,7 @@ features = ["suggestions", "color", "wrap_help"]
 
 [build-dependencies]
 clap = "2"
+output_vt100 = "0.1"
 
 [[bin]]
 name = "pastel"

src/cli/cli.rs

@@ -485,7 +485,7 @@ pub fn build_cli() -> App<'static, 'static> {
                 .value_name("mode")
                 .help("Specify the terminal color mode: 24bit, 8bit, off, *auto*")
                 .possible_values(&["24bit", "8bit", "off", "auto"])
-                .default_value("auto")
+                .default_value(if output_vt100::try_init().is_ok() {"auto"} else {"off"})
                 .hide_possible_values(true)
                 .hide_default_value(true)
         )

src/cli/main.rs

@@ -39,10 +39,6 @@ fn run() -> Result<ExitCode> {
 
     let interactive_mode = atty::is(Stream::Stdout);
 
-    if interactive_mode {
-        output_vt100::init();
-    }
-
     let color_mode = if global_matches.is_present("force-color") {
         Some(ansi::Mode::TrueColor)
     } else {