Marcus

@hwchase17 I'd appreciate this PR being merged as well. I'm wanting to do something similar to the sample @ulucinar posted earlier

@molan1976 Found these in api_fast.py: ``` presets = { 'ultra_fast': {'num_autoregressive_samples': 1, 'diffusion_iterations': 10}, 'fast': {'num_autoregressive_samples': 32, 'diffusion_iterations': 50}, 'standard': {'num_autoregressive_samples': 256, 'diffusion_iterations': 200}, 'high_quality': {'num_autoregressive_samples': 256, 'diffusion_iterations': 400}, }...