Focused and Pending specs + ObjectMatcher.toBeInstanceOf()

[peterklijn]

This PR covers issues:

• Object matcher suggestion: toBeInstanceOf #30 toBeInstanceOf() to ObjectMatcher.
• It should be possible to run a single or selection of tests instead of every test in a file #29 Running a single test or selection of tests.

It adds toBeInstanceOf() to object matcher:

expect("Hello Oleaster").toBeInstanceOf(String.class);

It adds the Jasmine style 'Focused specs', adding the ability to run a test or a set of tests on their own:

describe("Suite", () -> {
    it("will not run", () -> {
        assertTrue(false);
    });

    fit("will run", () -> {
        assertTrue(true);
    });
});

It adds the Jasmine style 'Pending specs', adding the ability to skip a test or set of tests:

describe("Suite", () -> {
    xit("will not run", () -> {
        assertTrue(false);
    });

    it("will run", () -> {
        assertTrue(true);
    });
});