1) Line up trailing dimensions in broadcast docs.
2) remove unnecessary expand_as in common_nn test.
3) use view in tensor_str instead of resize_.
4) newExpand remove raiseErrors change.
5) clarify expandedSizes/expandedStrides parameters in inferExpandGeometry.
6) simplify inferSize2/inferSizeN implementations.
7) use new-style classes for warning.
Setting torch.utils.backcompat.broadcast.warning.enabled=True
will cause Python warnings in the case where broadcast occurs
but previously 1-d view style pointwise ops occured.
