direnv cleanup.

Use the stdlib better.

.config/git/skel/.envrc

 # shellcheck shell=bash disable=SC1091
 # vim: ft=sh
+if ( cd .. && find_up .envrc >/dev/null )
+then
     source_up || true
-[ ! -f .envrc.private ] || . .envrc.private
+fi
+source_env_if_exists .envrc.private

Repositories/SchooLinks/.envrc

 # shellcheck shell=bash disable=SC1091
 # vim: ft=sh
+if ( cd .. && find_up .envrc >/dev/null )
+then
     source_up || true
+fi
 export AWS_DEFAULT_PROFILE=schoolinks
 export AWS_PROFILE=schoolinks
 export COMPOSE_FILE='docker-compose.local.yml'
 export GIT_AUTHOR_EMAIL='nimrod@schoolinks.com'
 export GIT_AUTHOR_NAME='Nimrod Adar'
 export PIPENV_VENV_IN_PROJECT=1
-[ ! -f .envrc.private ] || . .envrc.private
+source_env_if_exists .envrc.private