Replace karma/jasmine by jest

[alexjoverm]

Here you have a gift, you can take it or not :). Related to #12

Why to use Jest?

• (almost) No configuration. The only thing is the "jest" object in the package.json, and because it is typescript
• Combines under the hood jsdom, with jasmine and isparta
• Really fast (parallel exec)
• Amazing watch mode, try npm t -- --watch. Even you have the option to run only changed files, respect the latest git commit
• Coverage? just run npm t -- --coverage --no-cache (no-cache is suggested when running transformers like ts-lint)
• Great debugging and all kind of goodies

Basically, easier life 😎

[alexjoverm]

It seems like somehow I missed to add the right packages and types over there

[alexjoverm]

Hey @juristr! This PR has a dependency on https://github.com/DefinitelyTyped/DefinitelyTyped/pull/14867, that's why is failing since the spyOn is not in the @types. As soon as that PR get's merged I'll update this and let you know