fix: remove async/await API

[wale]

This PR removes the async/await API that was introduced when deeppyer used Microsoft's image API.

The programmatic API is now reduced to:

from PIL import Image
import deeppyer, asyncio

def main():
    img = Image.open('./foo.jpg')
    img = deeppyer.deepfry(img)
    img.save('./bar.jpg')

if __name__ == "__main__":
    main()

Closes #6