Add basic structure for unit tests

Introduce all the files necessary to load and test application modules
in a test environment. This allows the tests to be run via the command
line (by executing `grunt mocha`) or by opening the `index.html` file in
a web browser.
Enable livereload for unit tests via watch task
Add tests for BaseView module

...and remove the temporary "tautology" test file.
Reduce repetition in tests with Mocha `setup` hook
Introduce Sinon.JS testing utility

Unfortunately, the built library is not hosted on NPM or Bower, so we
need to manually download the source from the project website and check
it in to the repository.
Improve test maintainability with Sinon.JS stubs
Add tests for `BaseView#destroy`
Implement `BaseView#preDestroy` hook

Use a test-driven development approach to define acceptance criteria for
the method *before* writing the implementation. This aspect of our
process is not especially useful for other developers, so the individual
commits have been "squashed" together.