fish: ensure that /usr/local/bin is in the PATH

Signed-off-by: Christopher Larson <kergoth@gmail.com>
fish: ensure that /usr/bin/core_perl is in the PATH

Signed-off-by: Christopher Larson <kergoth@gmail.com>
fish: ensure that the pypy{,3} homebrew script dirs are in the PATH

Signed-off-by: Christopher Larson <kergoth@gmail.com>