Improve argument captors

[nhaarman]

At the moment the behavior of using argument captors differs between the Kotlin and Java versions.
For example, the below Kotlin test fails, while the corresponding Java test passes:

@Test
fun testKotlin() {
    /* Given */
    val date: Date = mock()

    /* When */
    date.time = 5L
    date.time = 7L

    /* Then */
    verify(date, times(2)).time = capture {
        expect(it).toBe(7L)
    }
}

@Test
public void testJava() {
    /* Given */
    Date date = mock(Date.class);

    /* When */
    date.setTime(5L);
    date.setTime(7L);

    /* Then */
    ArgumentCaptor<Long> captor = ArgumentCaptor.forClass(Long.class);
    verify(date, times(2)).setTime(captor.capture());
    assert captor.getValue() == 7L;
}

The reason is that the Java version matches the latest captured value, while the current Kotlin version matches the first.