title: GridFS.Upload() does not upload stream content
body: <p>Following example code:</p>
  
  <pre><code>using (var ms = new MemoryStream())
  {
      var artifactContent = Encoding.UTF8.GetBytes("content of some file/upload/etc as string");
      ms.Write(artifactContent, 0, artifactContent.Length);
  
      // ms.Lenght &gt; 0
  
  
      var gridFsCreateOptions = new MongoGridFSCreateOptions {ContentType = "text/plain"};
      var gridFsFileInfo = mongoGridFsDatabase.GridFS.Upload(ms, "Test.txt", gridFsCreateOptions);
  
      // stream is not uploaded and gridFsFileInfo.Lenght == 0
  }
  </code></pre>
  
  <p>The <code>fs.files</code> collection is filled, but the <code>fs.chunks</code> collection is empty.</p>
  
  <p>Whats wrong with my code?
  I'm using MongoDB 2.4.7 on Win8 and the official C# driver from NuGet.</p>