Add Plain markup implementation

Readme.md

@@ -5,7 +5,7 @@
 [![MIT licensed](https://img.shields.io/badge/license-MIT-blue.svg)](./LICENSE)
 [![Gitter chat](https://badges.gitter.im/gyscos/cursive.png)](https://gitter.im/cursive-rs/cursive)
 
-Cursive is a TUI (Text User Interface) library for rust. It is currently based on jeaye's [ncurses-rs](https://github.com/jeaye/ncurses-rs), but [other backends are available](https://github.com/gyscos/Cursive/wiki/Backends).
+Cursive is a TUI (Text User Interface) library for rust. It uses ncurses by default, but [other backends are available](https://github.com/gyscos/Cursive/wiki/Backends).
 
 It allows you to build rich user interfaces for terminal applications.
 

src/utils/markup/mod.rs

@@ -9,8 +9,9 @@ pub mod markdown;
 pub use self::markdown::Markdown;
 use owning_ref::OwningHandle;
 use owning_ref::StringRef;
-use std::marker::PhantomData;
 use utils::lines::spans::Span;
+use theme::Style;
+use std::borrow::Cow;
 
 /// Trait for parsing text into styled spans.
 pub trait Markup {
@@ -35,6 +36,20 @@ pub trait Markup {
     }
 }
 
+/// Dummy `Markup` implementation that returns the text as-is.
+pub struct Plain;
+
+impl Markup for Plain {
+    type Error = ();
+
+    fn parse<'a>(input: &'a str) -> Result<Vec<Span<'a>>, Self::Error> {
+        Ok(vec![Span {
+            text: Cow::Borrowed(input),
+            style: Style::none(),
+        }])
+    }
+}
+
 /// Holds both parsed spans, and the input string they borrow.
 ///
 /// This is used to pass around a parsed string.