[lmi] Failed vim-mode .zshrc experiment

[Greg Chicares]

Vadim--When convenient, would you please look at new branch odd/zsh_vim,
which has only one commit? I can't understand the behavior described,
and I'm hoping you'll quickly spot some obvious mistake. Commit message:

The intention is just to color $PROMPT based on zle $KEYMAP.
    
That intention is accomplished, but with a distressing side effect:
the Home and End keys no longer work as desired.
    
With this commit's parent, everything works: Home and End move the
cursor to the beginning and end of the line, respectively.
    
With this commit, neither Home nor End moves the cursor as expected.
Instead, Home enters 'vicmd' mode, and End followed by right-arrow
deletes to end of line.