Add Account class

web3.js/src/account.js

@@ -0,0 +1,21 @@
+import nacl from 'tweetnacl';
+import bs58 from 'bs58';
+
+export class Account {
+  constructor(secretKey: ?Buffer = null) {
+    if (secretKey) {
+      this._keypair = nacl.sign.keyPair.fromSecretKey(secretKey);
+    } else {
+      this._keypair = nacl.sign.keyPair();
+    }
+  }
+
+  get publicKey(): string {
+    return bs58.encode(this._keypair.publicKey);
+  }
+
+  get secretKey(): string {
+    return this._keypair.secretKey;
+  }
+}
+