Compacting the BitSet

[maciej]

Currently there is no way to compact the BitSet. The README.md states:

BitSets are never shrunk

I suggest adding a Compact method

func (b *BitSet) Compact() {}

which would compact the BitSet in place.

I'm willing to issue a PR as long as it gets reviewed and has a chance of getting accepted.

[lemire]

I'm willing to review it, and I am inviting the PR.

[maciej]

@lemire you can always be counted on when it comes to swift responses and good reviews!

[cristaloleg]

Any progress on this? 😺