refactor: Stimuli.core.Ajax
test: write Stimuli.core.Ajax tests
chore: add foo.json fixture
fix: Fix Exception handling in the entire framework
refactor: reviewed entirely the framework to be able to use stimuli this way

    (new Stimuli)

    .browser
        .navigateTo('http://yahoo.com')

    .mouse
        .click('#sometarget')
        .then(function() {
            var context = this.getWindow();
            expect(!!context.$)to.be(true);
        })
        .sleep(1000)
    .browser
        .navigateTo('http://google.com')

    .keyboard
    .typeText('hello world')

    .touch
        .rotate('#something')

    .destroy();