Fix make demo with project owners

The problem is that we weren't correctly storing the response
when creating users.  By storing the user object correctly,
we can then user the userid in subsequent tests.

Added 2 new tests for projectowner:
- make sure that we can't create an owner without a userId
- make sure that adding an owner succeeds with the right values.

This fixes #231
Merge pull request #238 from 18F/hotfix/make-demo-projowner

Fix make demo with project owners