Remove redundant bucket creation

Thanks for @HuEric! This commit is motivated by the issue #97.

example/simple_put/serverless.yml

@@ -15,6 +15,7 @@ custom:
   #            Properties:
   #                BucketName: ${self:service}-data
   s3:
+    host: localhost
     port: 8000
     directory: ./s3-local
     # Uncomment the first line only if you want to use cors with specified policy

index.js

@@ -229,7 +229,7 @@ class ServerlessS3Local {
         this.options.port = bindedPort;
         this.serverless.cli.log(`S3 local started ( port:${bindedPort}, family: ${family}, address: ${bindedAddress} )`);
 
-        this.createBuckets().then(resolve, reject);
+        resolve();
       });
       this.serverless.cli.log('starting handler');
       this.subscribe();