Fixed submitblock() - it now correctly uses share.BlockHex to submit.

Ever first block mined by CoiniumServ: https://chain.so/block/LTCTEST/71fdf5101d97bbf3a892b63d973bd78057dd645b556293373b0a89c49035c568
More ltc-testned blocks mined: https://chain.so/address/LTCTEST/n3Mvrshbf4fMoHzWZkDVbhhx4BLZCcU9oY