Avoid magic numbers (Ether address)

[ryu9827]

multisender/contracts/contracts/multisender/UpgradebleStormSender.sol

Line 103 in 17153e9

if (token == 0x000000000000000000000000000000000000bEEF){

multisender/contracts/contracts/multisender/UpgradebleStormSender.sol

Line 132 in 17153e9

Multisended(msg.value, 0x000000000000000000000000000000000000bEEF);

Suggest replace the address 0x000000000000000000000000000000000000bEEF with a constant variable. It improves readability and maintainability.