text: Title: Changing Tutorials to Colab Notebooks
  Body: ### Feature Description
  The source file for all the tutorials on the website (autokeras.com) should be a `.ipynb` file.
  
  ### Reason
  <!---
  Why do we need the feature?
  -->
  Make it easier for people to try out the tutorials.
  
  ### Solution
  <!---
  Please tell us how to implement the feature,
  if you have one in mind.
  -->
  Please help us change any of the `.md` files in the following directory to a `.ipynb` file.
  https://github.com/keras-team/autokeras/tree/master/docs/templates/tutorial
  
  You can refer to the `image_classification.ipynb` as an example.
  https://github.com/keras-team/autokeras/blob/master/docs/templates/tutorial/image_classification.ipynb
  
  Each pull request should only replace one file.