[Feature Request] Meta Learner Based code

[骑马小猫]

Introduction

After #23 merged, we can convert all of examples, under examples/image_classification, to meta learner based examples.

I have an online meeting with @tata1661 before, and we believe that it will be more concise if the model-zoo examples be replaced with meta learner (optim-based) . Let's get it on the way.

[Yaqing Wang]

@wj-Mcat Nice work! Many thanks!