git subrepo pull vendor/registripe

Also update vendored_requirements to make sure we pull this in.

subrepo:
subdir: "vendor/registripe"
merged: "9fc3645"
upstream:
origin: "git@gitlab.com:tchaypo/registrasion-stripe.git"
branch: "lca2018"
commit: "9fc3645"
git-subrepo:
version: "0.3.1"
origin: "???"
commit: "???"