Preparation for open sourcing

[GSGerritsen]

For DEV-7299:

• updated documentation copy throughout codebase
• removed combinatorial.rs (PR is ready for rust-bfield once this is on crates.io)
• updated benchmarks to use a small local test bfield file instead of the massive one on s3 (users should be able to just run cargo bench instead of fetching an additional file)
• very minor code updates
• readme update (more elaborate examples + license section)
• minor LICENSE update

[linear[bot]]

DEV-7299 Open source mmap-bitvec

🦀🦀🦀

[Keats]

There's a fair amount of unsafe usage. @Keats what do you think is the most elegant way to document this in the code? And any obvious opportunities to reduce without performance impact?

We would need some time to set up lots of benchmarks and test things. We can do that later once it's open-source (or maybe someone will be horrified by the unsafe and will fix it for us!)

[boydgreenfield]

@GSGerritsen @Keats All you to merge and release when you want then!