Fixed typo in docs

docs/index.md

@@ -53,7 +53,7 @@ var privateKey = new bitcore.PrivateKey();
 var exported = privateKey.toWIF();
 // e.g. L3T1s1TYP9oyhHpXgkyLoJFGniEgkv2Jhi138d7R2yJ9F4QdDU2m
 var imported = bitcore.PrivateKey.fromWIF(exported);
-var hexa = exported.toString();
+var hexa = privateKey.toString();
 // e.g. 'b9de6e778fe92aa7edb69395556f843f1dce0448350112e14906efc2a80fa61a'
 ```
 

lib/privatekey.js

@@ -282,7 +282,7 @@ PrivateKey.isValid = function(data, network){
  */
 PrivateKey.prototype.toString = function() {
   return this.toBuffer().toString('hex');
-}
+};
 
 /**
  * Will output the PrivateKey to a WIF string