institutions and harvest feeds

Institutions and harvest feeds (user-entered data meant primarily for human consumption)
 - basic models, controllers, views, routes, and migrations
 - rake tasks to save and delete sample institution and harvest feed

For reference, the ER diagram is here: https://docs.google.com/a/dp.la/drawings/d/1Wmtq6x_VBjJGgwAMhT2qUHvkuQAygMLooXd0K2eOAPo/edit

You can test in your browser by following the README instructions to generate and start a dummy application, and then creating a sample institution.  Go to `http://localhost:3000/krikri/institutions`.  You should see one institution listed.  A link from that page should take you to a view with data for that institution.  From there, another link should take you to a view with data for one sample harvest feed.

Once @mb has customized the user model, we can integrate it with the institution model and possibly rethink the routes to fit with admin and general user dashboards.
Fixed with this commit: https://github.com/dpla/KriKri/commit/9af7e50ca85a7be49105e3a83fc9751ab3ad11d9