Fixed build error

.travis.yml

@@ -1,6 +1,6 @@
 language: node_js
 node_js:
-- '6'
+- '8'
 branches:
   except:
   - releases
@@ -21,7 +21,7 @@ addons:
   sauce_connect: true
   chrome: stable
 cache: yarn
-before_install: if [[ `npm -v` != 3* ]]; then npm i -g npm@3; fi
+before_install: if [[ `npm -v` != 6* ]]; then npm i -g npm@6; fi
 before_deploy:
 - if [[ ! -z "$TRAVIS_TAG" ]]; then npm run build:all; fi
 deploy:

package.json

@@ -7,8 +7,8 @@
     "url": "git://github.com/Rebilly/ReDoc"
   },
   "engines": {
-    "node": ">=6.9",
-    "npm": ">=3.0.0"
+    "node": ">=8.10.0",
+    "npm": ">=6.3.0"
   },
   "main": "dist/redoc.module.js",
   "module": "dist/redoc.module.js",
@@ -105,7 +105,7 @@
     "style-loader": "^0.18.2",
     "swagger-schema-official": "^2.0.0-bab6bed",
     "tslint": "^5.7.0",
-    "typescript": "^2.5.2",
+    "typescript": "2.9",
     "webpack": "^3.6.0",
     "webpack-dev-server": "^2.8.2",
     "webpack-merge": "^4.1.0"