when I try to upload a large file, localstack basically freezes (and eventually times out).  
But if the file is all `1` bytes it succeeds.

succeeds:
```bash
aws s3 --endpoint-url=http://localhost:4572 mb s3://testbucket
python -c "print '\x01'*10000000" > testfile
echo $(ls -ahl | grep testfile)
aws s3 --endpoint-url=http://localhost:4572 cp testfile s3://testbucket/testfile
```

fails:
```bash
aws s3 --endpoint-url=http://localhost:4572 mb s3://testbucket
python -c "print 'a'*10000000" > testfile
echo $(ls -ahl | grep testfile)
aws s3 --endpoint-url=http://localhost:4572 cp testfile s3://testbucket/testfile
```
so, for me, both the file content and its size determine if this triggers or not. 
I'm using the latest version `0.9.5`
key_by_path = 'key-by-hostname'
        queue_url, queue_attributes = self._create_test_queue()
        self._create_test_notification_bucket(queue_attributes)
        
        self._perform_multipart_upload(bucket=TEST_BUCKET_WITH_NOTIFICATION, key=key_by_path, zip=True)
        self.assertEqual(self._get_test_queue_message_count(queue_url), '1')
        
        self.sqs_client.delete_queue(QueueUrl=queue_url)
        self._delete_bucket(TEST_BUCKET_WITH_NOTIFICATION, [key_by_path])
    def test_s3_multipart_upload_acls(self):
        bucket_name = 'test-bucket-%s' % short_uid()
        self.s3_client.create_bucket(Bucket=bucket_name, ACL='public-read')
        def check_permissions(key, expected_perms):
            grants = self.s3_client.get_object_acl(Bucket=bucket_name, Key=key)['Grants']
            grants = [g for g in grants if 'AllUsers' in g.get('Grantee', {}).get('URI', '')]
            self.assertEquals(len(grants), 1)
            permissions = grants[0]['Permission']
            permissions = permissions if isinstance(permissions, list) else [permissions]
            self.assertEquals(len(permissions), expected_perms)
        
        self.s3_client.put_object(Bucket=bucket_name, Key='acl-key0', Body='something')
        check_permissions('acl-key0', 1)
        self._perform_multipart_upload(bucket=bucket_name, key='acl-key1')
        check_permissions('acl-key1', 1)
        self._perform_multipart_upload(bucket=bucket_name, key='acl-key2', acl='public-read-write')
        check_permissions('acl-key2', 2)
    def test_s3_presigned_url_upload(self):