`read()` - unused and appears not to work

[clach04]

https://github.com/ikalchev/py-sds011/blob/4d3380a166c90fc1750f70b84beb3bc1f75dee66/sds011/init.py#L158

Wondering if a PR to remove this is a good idea. I spent some time with this and couldn't get it to work. Documented query() worked fine.

[romintomasetti]

I think that read() is to be used in active reporting mode.