New test setup

A variety of changes that result in a new and improved (IMO) test setup:

* Configure Travis CI to install Bower and Bower packages before running tests.
* Remove all Grunt dependencies in favour of the Karma test runner.
* Very small tweaks to the tests so that they play well with Karma.
* Add development notes to the README so others can get the test environment setup.
* Some small cleanup tasks in the docs.

Hopefully the README instructions are clear enough that you can get the test environment up and running and see that the tests pass in real browsers, as well as CI (`npm test`).

I think this is a more lightweight and reliable setup. Let me know what you think.