* Add a Karma configuration for unit/integration tests
for the client-side pywb code.
* Add an integration test suite which creates an <iframe> loads
the client-side rewriting code (wombat.js) in it and
then executes a test script.
Since wombat.js monkey-patches the DOM and the exact behavior
of DOM objects varies between browsers, which we want to test,
the suite does not mock the DOM but instead runs
a set of tests in an isolated environment against
the DOM.
* Add Travis config to run the Karma tests
