message: move react-router-dom to devDeps
diff: "classnames": "^2.2.5",
  "d3-shape": "^1.2.0",
  "react": "^16.2.0",
  - "react-router-dom": "^4.3.1",
  "system-classnames": "^1.0.0-3"
  },
  "devDependencies": {
  "babel-preset-env": "^1.6.1",
  "babel-preset-react": "^6.24.1",
  "jest": "^22.4.3",
  + "react-router-dom": "^4.3.1",
  "react-test-renderer": "^16.3.2",
  "styled-components": "3.3.2",
  "styled-system": "^2.0.2"
  