changelog for v88

changelog v87

v86 changelog

changelog piped output buffer fix

changelog sed replacement

v83 changelog

Merge pull request heroku#267 from heroku/detect-errors

Detect errors

Merge pull request heroku#265 from heroku/performance-l

Performance L

Merge pull request heroku#258 from SonicHedgehog/node-env-runtime

Default to NODE_ENV=production during runtime

Merge pull request heroku#257 from heroku/performance-m-dynos

test and implementation for performance m dynos