title: mongoengine save method is deprecated?
body: <p>I wonder why my python says that mongoengine save() method is deprecated? I don't see any info about this into official documentation <a href="https://mongoengine.readthedocs.io/en/v0.9.0/apireference.html" rel="nofollow noreferrer">https://mongoengine.readthedocs.io/en/v0.9.0/apireference.html</a></p>
  
  <pre><code>class MyModel(Document):
      user_id = StringField(required=True)
      date = DateTimeField(required=True, default=datetime.datetime.now)
  
  my = MyModel()
  my.user_id = 'user'
  my.save()
  </code></pre>
  
  <p>and now i see: </p>
  
  <blockquote>
    <p>/Library/Python/2.7/site-packages/mongoengine/document.py:340:
    DeprecationWarning: save is deprecated. Use insert_one or replace_one
    instead</p>
  </blockquote>
  
  <p>I've python 2.7 and also installed pymongo, mongoengine and bottle-mongo (maybe some issues with that?)</p>