Add symlinks for neovim compatibility.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
zsh: add color_fg_ansi.

This function produces the portion of an ANSI code that can be used in
LS_COLORS or GREP_COLORS.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
zshrc: set GREP_COLORS to be more readable.

Magenta on a semi-transparent background is hard to read.  Use a
brighter blue instead.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>