Change minter address

[17number]

Fix #37

$ node
Welcome to Node.js v12.7.0.
Type ".help" for more information.
> const libra_core = require("libra-core");
undefined
> const LibraWallet = libra_core.LibraWallet;
undefined
> const LibraAccount = libra_core.Account;
undefined
> const LibraClient = libra_core.LibraClient;
undefined
> const LibraNetwork = libra_core.LibraNetwork;
undefined
> const wallet = new LibraWallet();
undefined
> const account = wallet.newAccount();
undefined
> const client = new LibraClient({ network: LibraNetwork.Testnet });
undefined
> client.mintWithFaucetService(account.getAddress(), 1e6).then(r => console.log(r)).catch(e => console.error(e));
Promise { <pending> }
135

[perfectmak]

Thank you for the contribution. I'll review and publish a release later today.