changes for issue 178, change to DefaultMockingDetail and a simple test

A simple implementation for [Issue 178](https://code.google.com/p/mockito/issues/detail?can=2&start=0&num=100&q=&colspec=ID%20Type%20Status%20Priority%20Milestone%20Owner%20Summary&groupby=&sort=type&id=178)

Modified the MockingDetails API to expose a getInvocations() method. This uses the invocation container from the MockUtil object to return a collection of Invocations (which is in the org.mockito.invocation package). This enables users to debug and see invocations on a given mock and use the debugger (or code) to see arguments passed, the target method, etc.