perturb

use own flatMap for now, for node 10

Merge pull request #14 from bttmly/dependabot/npm_and_yarn/diff-3.5.0

Merge pull request #13 from bttmly/dependabot/npm_and_yarn/mixin-deep-1.3.2

Bump diff from 1.4.0 to 3.5.0

Bump mixin-deep from 1.3.1 to 1.3.2