refactor table render; fix backspace; only works in col 0?

src/main.rs

@@ -1,6 +1,7 @@
 #![allow(stable_features)]
 #![feature(os_str_display)]
 #![feature(str_as_str)]
+#![feature(let_chains)]
 
 use std::sync::{Arc, RwLock};
 use std::path::{Path, PathBuf};