Draft: Transpose matrices

should address #4

changelog

• transpose all random matrices when they are created, i.e. using Matrix::random(n, k) instead of Matrix::random(k, n)
• transpose the Vandermonde matrix definition
• add a Matrix::get_row method
• fix the linalg tests
• show the exact error in FEC tests
• do not transpose in fec::encode and fec::decode
• add test assertion to make sure fec::encode always generates n shards
• add some runtime assertions

tests

cargo t -- linalg fec

passes