Need to complete the unit tests for JSONPointer #590

See the discussion about unit tests in #588. The code has been merged, but should not be released until all of the suggested unit tests have been implemented. Unit tests that are mentioned in the comments and already in place should be refactored if they do not clearly show the expected result in the code. For example, this code:

    @Test
    public void objectPropertyQuery() {
        assertSame(document.get("foo"), query("/foo"));
    }

Could be refactored to:

    @Test
    public void objectPropertyQuery() {
        assertSame(document.get("foo"), query("/foo"));
        assertEquals(query("/foo").toString(), "[\"bar\",\"baz\"]");
    }