title: Mongoengine LongField Overflow Error
body: <p>I have a Text model;</p>
  
  <pre><code>class Text(db.Document):
      siphash_value = db.LongField()
  </code></pre>
  
  <p>Then I use siphash lib for create a hash.(<a href="https://github.com/majek/pysiphash" rel="nofollow">https://github.com/majek/pysiphash</a>)</p>
  
  <p>This lib converts string to long value like <strong>12398370950267227270L</strong></p>
  
  <p>If I try save document to my db;</p>
  
  <pre><code>Text(siphash_value=12398370950267227270L).save()
  </code></pre>
  
  <p>I get this error:</p>
  
  <pre><code>OverflowError: MongoDB can only handle up to 8-byte ints
  </code></pre>