Describe disabling key-chords in the README

It's good to have defaults, but nice to document a way of changing them
as well.
Merge pull request #324 from Abizern/key_chord_documentation

Describe disabling key-chords in the README
Remove problematic kk keychords
Override default move-beginning-of-line behavior
Add missing whitespace
Enable manually elisp-slime-nav (fixes #325)
Merge commit 'fb1164e37f8824c4e3c70c4fc17d823aa4116694' into rock-mac
Updated ESS submodule