Updated zsh's PROMPT and RPROMPT.
Updated zsh's PROMPT and RPROMPT.

PROMPT now indicates if the current shell was started within vim by the
:sh command.

RPROMPT now only replaces "$HOME" with "~" instead of replacing all
substrings of the current path with any matching environment variables.

BradBuckingham/dotfiles,BradBuckingham/dotfiles,BradBuckingham/dotfiles