added unit tests for block gauss-seidel
added unit tests for block gauss-seidel

kidaa/pyamg,huahbo/pyamg,pyamg/pyamg,pyamg/pyamg,huahbo/pyamg,huahbo/pyamg,huahbo/pyamg,kidaa/pyamg,pyamg/pyamg,kidaa/pyamg,kidaa/pyamg