refactor: npm and semver (#1817)

lib/config/validation.js

lib/datasource/github.js

lib/manager/_helpers/node/package.js

lib/manager/bazel/package.js

lib/manager/docker/package.js

lib/manager/npm/package.js

lib/manager/npm/versions.js

lib/manager/travis/package.js

lib/util/semver.js

lib/workers/pr/changelog.js

test/manager/npm/__snapshots__/versions.spec.js.snap

test/manager/npm/package.spec.js

test/manager/npm/versions.spec.js

test/util/semver.spec.js