Pettanko - stripped down version of osu! performance calculators.

It's Pettanko because you can't name something related to pp calculation without using some kind of a japanese boobs word.
And also because it's slim.

How to use

1. Add it to your project using Nuget
2. Get beatmap difficulty attributes from osu! API v2
3. Call Pettanko.Calculate(DifficultyAttributes difficultyAttributes, Score scoreData)

Calculators don't need anything other than difficulty attributes and score data. No beatmap means no slow parsing.