Missing card_info_lut.joblib

[GaussianZero]

Is your feature request related to a problem? Please describe.
I think the documentation is a little unclear that poker_ai cluster needs to be run first. I'd recommend making that more clear in the Readme.md (I think if you read the whole file, and read between the lines, you can understand it). It should be clearer to new readers to help beginners get started (you'll get more usage out of the library).

Additionally, if one runs poker_ai train start and card_info_lut.joblib doesn't exist, I think it would be better to give the user an actionable error message (like "perhaps you need to run run poker_ai cluster first", rather than just an error that the file doesn't exist). Sure, of course the file doesn't exist, but what should I, as a new user, do to fix that?