Enable tests for proxy handler

Updating the swagger spec file is fine, we just need to be intentional about changes we make to it -- it's meant to specify the API, rather than reflect it.

For now, the (informal) process is:

1. Write new tests in *restbase/test/*
1. Implement necessary changes to pass the tests
1. Vet everything through a PR
1. Once it's all been merged, consider moving it from the tests to the swagger file
  * This will affect all branches, so should only be done when we expect every branch to pass the new tests
  * Updating the swagger file is done by editing it in the *gh-pages* branch