Mockito optional matchers

[xsveda]

Custom Mockito ArgumentMatcher for Optional that can be used to for enhanced stubbing and verification.
Example:

        Foo foo = mock(Foo.class);
        when(foo.bar(anyPresentOptional())).thenReturn(true);
        when(foo.bar(anyEmptyOptional())).thenReturn(false);

New Mockito matchers are placed in mockito sub-package. It might make sense to move existing Hamcrest matchers to hamcrest sub-package (that would be an API breaking change) or make a standalone test modules: streamTestHamcrest and streamTestMockito. What do you think @aNNiMON ?

[coveralls]

Coverage decreased (-5.6%) to 94.444% when pulling 1316b1d on xsveda:mockito_optional_matchers into f35bcc0 on aNNiMON:master.

[coveralls]

Coverage remained the same at 100.0% when pulling 6bae410 on xsveda:mockito_optional_matchers into f35bcc0 on aNNiMON:master.

[aNNiMON]

@xsveda thank you for your pull request. For me, creation of new submodules for each test framework is not necessary, and classes had to be moved to hamcrest package in any case. I'll do it soon.