First pass keymap implementation
Add commands for move-to-line-end/start
Tweak the `Command` enum, add a few Ctrl keys
Rebase, move binding initialization to keymap
Move all key bindings into KeyMap
Ctrl-H should delete to the left, not the right
Rebased, use `cursor()` and `Arc<AtomicBool>`
Merge pull request #31 from Crespyl/keymap

Implemented keymap