Add `SelectBase.scalars()`
There are a few issues with your patch - it consumes the entire cursor in one go and returns a list, when it would probably be better suited to use a generator. Similarly, it is not carrying through the `database` parameter. I will implement a similar patch and merge it. Thank you!
Mr. Leifer, thanks for creating and maintaining such a great library. We've used peewee at Propel since 2015.

This PR adds `SelectBase.scalars()`, which is something we've wanted for a while. `scalar()` is very convenient, and we thought something similar for multiple values would be too. I've proposed `scalars()` as the name, but would be happy to settle on something else if you prefer.

Thanks for considering.