Bump acorn from 6.3.0 to 6.4.2#30

dependabot[bot] wants to merge 1 commit intomasterreshufflehq/slack-url-shortener:masterfrom

dependabot/npm_and_yarn/acorn-6.4.2reshufflehq/slack-url-shortener:dependabot/npm_and_yarn/acorn-6.4.2Copy head branch name to clipboard