Add testing info to docs

[mAAdhaTTah]

Adding information on how to test Kefir Observables would be a nice addition to the docs. Wondering if we should put all of that into the main docs site, or have a separate site for testing with chai-kefir, or maybe moving all the docs into a kefirjs.github.io repo & website. Thoughts?

[rpominov]

I'd probably put testing documentation into chai-kefir readme.

As for separate repo for the docs, I think it's great idea. Might be tricky to separate from the main repo though.