#4 Simplify MockObjectFactory#injectMock to only one interface

[Brian Freeman]

The new method added to the MockObjectFactory in r3-1-1 allows the specification of multiple interface classes using the Java 1.5 ellipses capability:
injectMock(Object objToInjectTo, String fieldToInjectTo,
Class ... interfaceToMock)

Want to remove the ellipses to just allow the specification of one interface class for two reasons:
1) After thinking about it for a minute, I couldn't think of a scenario where it would make sense to use this method with multiple interface classes anyway. All cases it should just be implementing the single interface that the MockObject is being injected into.
2) This isn't very 1.4 friendly so using the method requires the use of one interface class to be wrapped with new Class[] {MyInterface.class}