Add step to setup in README

[martiansnoop]

No description provided.

[cjroth]

@h4xnoodle I think you are right, but I will also add that I'm using gulp-karma and with my setup, I had to add it to the plugins explicitly even though it's prefixed with karma-.

[kobrigo]

It did not work for me. karma did not load the siblings automatically. I had to add karma-fixture and also karma-html2js-preprocessor.

[billtrik]

@kobrigo what was your setup?

I tried it on a clean, default karma setup (npm packages), and it was loaded without having to declare it
in the plugins array. All it took was the directory to exist inside $./node_modules/, and to declare the plugin inside the frameworks array.

Although since it might be a problem in other setups, for example gulp, it makes sense to add it.
I will tag it with something like "if it doesn't work for you, then.."