Add math styling module

Cargo.toml

@@ -9,3 +9,7 @@ readme = "README.md"
 license = "Apache-2.0"
 categories = ["encoding", "text-processing"]
 keywords = ["unicode", "symbols"]
+
+[features]
+default = ["styling"]
+styling = []

src/lib.rs

@@ -11,6 +11,9 @@ pub use self::shared::ModifierSet;
 
 mod shared;
 
+#[cfg(feature = "styling")]
+pub mod styling;
+
 /// A module of definitions.
 #[derive(Debug, Copy, Clone)]
 pub struct Module(&'static [(&'static str, Binding)]);