Issue #3606 .

Changes are mainly:

1. in THBlas.c, use assert rather than if.
2. in relevant caller functions in THTensorMath.c, make tensors contiguous if those checks aren't met.
3. add contiguity checks in 4 legacy kernels ([Spatial|Volumetric](Full)?DilatedConvolution) that calls these methods. They are contiguous before, but the logic involves both Python and C++, and is a bit complicated, so I add the check to be clear, and to be safe.