Add power-user docs to bounter.py

[piskvorky]

Expand on the way the algos work under the hood, for power users: parameters of CMS (width, depth), memory vs accuracy trade-offs, log8/log1024 etc.

This should be either a part of bounter.py module docstring (where people are most likely to look for it; we also link to this from the README), or a link to a repo notebook / .md file linked to from bounter.py docstring.

[thoppe]

Related to this, looking at the docs for the parameter:

size_mb (int): Desired memory footprint of the counter.

It's unclear what the default size is. If left to None, does it expand to available memory (this is what I'm assuming)?

[aneesh-joshi]

@thoppe
https://github.com/RaRe-Technologies/bounter/blob/1585aff2afb20dca5bb7115e119497a7c22f1d2b/bounter/bounter.py#L32-L33

doesn't seem to do anything but raise an error.

@piskvorky we should probably also move the docs style to be more like numpy docs (like is being done in gensim) wdyt?

[piskvorky]

Yeah, why not.

But either way we should make clear what parameters are mandatory (size_mb) and which are optional, with what defaults.