0.16.0

This is an important addition by Tomasz @tszumski. It passed all existing tests, and accomplishes the following:

• It adds AVX2 support for block encoding and decoding.
• It also fixes what I think is a bug in AVX512 block encoding.

According to Tomasz tests, we get
Encoder: performance gain ~37% vs C-code, (~7.5% performance drop vs AVX512-code​)
Decoder: performance gain ~7%

What's Changed

• Add avx2 optimization for encoder and decoder by @tszumski in #153

New Contributors

• @tszumski made their first contribution in #153

Full Changelog: 0.15.0...0.16.0