Summary:
Currently, Celerity map rebuilds on Windows don't put Stripe or Raphael into the map. Move them into `webroot/rsrc/externals/` so they get picked up.
At some point we should maybe let the mapper load resources from mulitple locations, but this is more straightforward for now.
See https://github.com/facebook/phabricator/issues/294
Test Plan: Rebuilt map, verified Burnup Rate + Stripe work.
Reviewers: vrana, btrahan
Reviewed By: btrahan
CC: aran
Differential Revision: https://secure.phabricator.com/D5661
