Introduce jest as test-framework for gui code (react).

jest is somewhat documented here:
https://facebook.github.io/jest/

related to #61
Merge pull request #65 from finn-no/feature/jest-gui-testing

Introduce jest as test-framework for gui code (react).
Begin work on running tests against the database:

* Add Travis postgresql setup.
* Replace "db mocks" with a before hook that creates the same data
  through the HTTP API.
* Reset DB and re-create all fixtures for each test. We'll need
  something  better here.
* CAVEAT: no concept of a dev vs test database. Running tests will
  clear data from the currently configured database.
Remove unused code