add karma for automated launching of browser test

[kfarr]

Right now as a user you must manually navigate to a test URL in the browser when running the local dev server: http://localhost:3333/test/browserTests/street-geo-test.html

Instead, this should be opened with an appropriate npm command on the terminal

To get started, you can check out karma.conf.js in some other projects liked networked a-frame: https://github.com/networked-aframe/networked-aframe/blob/master/tests/unit/karma.conf.js