Implemented the 'any' operator

This implements the operator `Any` from #24 in all two variants.

However, I encountered two problems.

I'm confused by `True if all elements of an observable sequence satisfies a condition; otherwise, false.` in [MSDN](http://msdn.microsoft.com/en-us/library/hh211993(v=vs.103\).aspx). I'm not sure how to handle an  observable sequence. I can not test it by myself as I does not have the C# environment in my hand. At last, in my implementation, if an observable sequence is empty, `any` always emits `false`. It may confuse people who are familiar with FP.

Another question is if I add the `any` method to `rx.Observable<T>`, some unit tests will fail as the method `any` in  `rx.Observable<T>` overrides the method `org.mockito.Matchers.any(java.lang.Class<T>)` in some unit tests (e.g., `rx.subjects.ReplaySubject<T>`). Do I need to use another method name, or just modify the unit tests? Now the `any` methods in `rx.Observable<T>` are commented out.

Thanks.