remove unused base58check dependency

lib/expmt/stealthkey.js

@@ -4,7 +4,6 @@ var Pubkey = require('../pubkey');
 var Point = require('../point');
 var Hash = require('../hash');
 var KDF = require('../kdf');
-var base58check = require('../base58check');
 
 var Stealthkey = function Stealthkey(payloadKeypair, scanKeypair) {
   if (!(this instanceof Stealthkey))

test/stealthkey.js

@@ -5,7 +5,6 @@ var Privkey = require('../lib/privkey');
 var Pubkey = require('../lib/pubkey');
 var BN = require('../lib/bn');
 var Hash = require('../lib/hash');
-var base58check = require('../lib/base58check');
 
 describe('Stealthkey', function() {