Remove butternut

[srod]

Fix #345

[codecov]

Codecov Report

Merging #400 into 4.0 will decrease coverage by 0.06%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             4.0     #400      +/-   ##
=========================================
- Coverage   97.6%   97.53%   -0.07%     
=========================================
  Files         18       17       -1     
  Lines        292      284       -8     
  Branches      63       61       -2     
=========================================
- Hits         285      277       -8     
  Misses         7        7

Impacted Files	Coverage Δ
lib/compress.js	100% <ø> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update b5f99cd...a8a90c5. Read the comment docs.