ENH: tm.assert_(is|not)_copy, tm.shares_memory

[jbrockmendel]

There are a number of places in the tests where we check that a result is a copy, is not a copy, is a view, is not a view, etc. We end up with ad-hoc implementations all over the place. It'd be nice to have a something like assert not tm.shares_memory(series, series.copy()). This would likely require EA authors to implement parts of it.

[jbrockmendel]

tm.shares_memory exists, though not used much. closing.