title: write persisted keras model to s3
body: <p>I ran an lstm model in keras and persisted it to a json object. 
  I want to write this json object directly to an s3 bucket. Boto3 tutorials really don't cover this, they only show how to write files to s3. I really need to be able to store keras models in json directly from python (in memory) to s3. Any ideas?</p>