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`
bucket_name = 'test-bucket-%s' % short_uid()
        self.s3_client.create_bucket(Bucket=bucket_name)
        
        object_key = 'key-by-hostname'
        self.s3_client.put_object(Bucket=bucket_name, Key=object_key, Body='something')
        
        url = self.s3_client.generate_presigned_url(
            'get_object', Params={
                'Bucket': bucket_name,
                'Key': object_key,
                'ResponseCacheControl': 'max-age=74',
                'ResponseContentDisposition': 'attachment; filename="foo.jpg"',
                'ResponseContentEncoding': 'identity',
                'ResponseContentLanguage': 'de-DE',
                'ResponseContentType': 'image/jpeg',
                'ResponseExpires': 'Wed, 21 Oct 2015 07:28:00 GMT'}
        )
        response = requests.get(url, verify=False)
        self.assertEqual(response.headers['cache-control'], 'max-age=74')
        self.assertEqual(response.headers['content-disposition'], 'attachment; filename="foo.jpg"')
        self.assertEqual(response.headers['content-encoding'], 'identity')
        self.assertEqual(response.headers['content-language'], 'de-DE')
        self.assertEqual(response.headers['content-type'], 'image/jpeg')
        self.assertEqual(response.headers['expires'], '2015-10-21T07:28:00Z')
        
        self._delete_bucket(bucket_name, [object_key])
    def test_s3_copy_md5(self):