factor input handling into modes

src/keys/save.rs

@@ -0,0 +1,10 @@
+use crate::*;
+
+impl Taggart {
+    pub fn mode_save (&mut self, event: &Event) {
+        todo!()
+    }
+    pub fn save_begin (&mut self) {
+        self.mode = Some(Mode::Save { value: false })
+    }
+}