js: Add identifiers to X-Editable templates.

This gives the form elements name and id attributes, as appropriate.
This will make it easier for us to refer to them in integration tests.
workbench: Add Capybara gem for integration tests.
workbench: Add integration test helper module.

This provide a base test class that provides the Capybara DSL and a
couple of convenience methods.  It also specifies a test runner class
that sets up the API server consistently, with the proper environment.
workbench: Use Poltergeist for integration tests.

This is faster and will enable us to run integration tests on the
build server.

PhantomJS (http://phantomjs.org/) has to be installed in the $PATH for
this to work.
workbench: Add VM integration tests.

This is the "start test" that Ward suggested I implement to start off.
It's easy but not trivial: it requires JavaScript support and filling
out a form.
workbench: Add basic login integration tests.
workbench: Document integration test dependencies.

This adds appropriate notes to the installation guide, and suggestions
to application.yml.example.
workbench: Make integration test settings default.

We know that these settings should work out of the box, given the
settings in the API server's `rails` script.  Making them the default
makes it easier to get the tests running.
workbench: Fix typo in application.default.yml.
Merge branch '2288-integration-tests'