actually use the text library for text editing (fully working I think but code isn't cleanest)

src/lib.rs

@@ -5,6 +5,8 @@
 #![feature(map_try_insert)]
 #![feature(trait_alias)]
 #![feature(round_char_boundary)]
+#![feature(unboxed_closures)]
+#![feature(fn_traits)]
 
 pub mod core;
 pub mod layout;