no need to store these things in the slug

better caching for yarn

check on yarn production incompatibility with npm

ignore engine incompatibilities, this is a dev warning

check npm incompatibility

margins around warning

combined if

tests and implementation for using yarn in place of npm

leave node_modules for caching

use pure-lockfile

use semver.io service to resolve yarn engines

restore original yarn.lock after yarn install

use mktemp compatible with both osx and linux

use yarn check before a --pure-lockfile

use yarn check before a --pure-lockfile

remove yarn check, does not work as documented

clear prebuilt node_modules for yarn users

initial implementation for bin/test and bin/test-compile

changelog for v91

remove hard max of 32 processes

remove debugging log for devdeps

Extended warnings

correct GitHub capitalization

remove npm prune to work around shrinkwrap issues

output stream errors should not fail the build