Move customizations for keys to the minor mode map (closes #6)
Update README

 - The convention of uppercase special keys is gone, replaced with
   simpler text about `G`

 - Updated example of repetition to show why you would use it.

 - Fixed outdated `C` for C-c C-

 - Changed example of `i` -> `C-i` since that is actually `TAB`

 - Added mnemonic advice for `i`