TST: sparse: add explicit zeros to matrices used in noncanonical format tests
TST: sparse: dense RHS/LHS are supported in comparisons for Numpy >= 1.8, so enable the tests
BUG: sparse: fix bugs in __eq__ with explicit zeros, and fix nan comparisons
Merge pull request #3813 from pv/csr-comparison-fail

BUG: sparse: fix __eq__ for matrices with explicit zeros