Breaking changes: rename getters/setters

Rename `get_history` to `history_mut`
Rename `get_history_const` to `history`
Replace `set_completer` by `set_helper`
diff --git a/src/lib.rs b/src/lib.rs
index 5e76b3a..519329c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -724,12 +724,12 @@
     }
 
     /// Return a mutable reference to the history object.
-    pub fn get_history(&mut self) -> &mut History {
+    pub fn history_mut(&mut self) -> &mut History {
         &mut self.history
     }
 
     /// Return an immutable reference to the history object.
-    pub fn get_history_const(&self) -> &History {
+    pub fn history(&self) -> &History {
         &self.history
     }
 
@@ -739,11 +739,6 @@
         self.helper = helper;
     }
 
-    #[deprecated(since = "2.0.0", note = "Use set_helper instead")]
-    pub fn set_completer(&mut self, completer: Option<H>) {
-        self.helper = completer;
-    }
-
     /// Bind a sequence to a command.
     pub fn bind_sequence(&mut self, key_seq: KeyPress, cmd: Cmd) -> Option<Cmd> {
         let mut bindings = self.custom_bindings.write().unwrap();