Update karma config to allow requiring of additional bower components

I ran into an issue when attempting to add another bower component and referencing it in my component test - I got an error only in the test "ERROR: 'There is no timestamp for /base/app/bower_components/handlebars/handlebars.js!'"  from karma.  It's a confusing error, and I think we should by default include bower components in karma so that you can require stuff in your app code and it won't break tests - and the solution to that would be to just have karma load all the bower components anyways, I think.