chore: bump version to v1.18.1-post (#4630)

docs/api.md

@@ -1,6 +1,8 @@
 
-# Puppeteer API <!-- GEN:version -->v1.18.1<!-- GEN:stop-->
-<!-- GEN:empty-if-release --><!-- GEN:stop -->
+# Puppeteer API <!-- GEN:version -->Tip-Of-Tree<!-- GEN:stop-->
+<!-- GEN:empty-if-release -->
+#### Next Release: `July 18, 2019`
+<!-- GEN:stop -->
 
 - Interactive Documentation: https://pptr.dev
 - API Translations: [中文|Chinese](https://zhaoqize.github.io/puppeteer-api-zh_CN/#/)

package.json

@@ -1,6 +1,6 @@
 {
   "name": "puppeteer",
-  "version": "1.18.1",
+  "version": "1.18.1-post",
   "description": "A high-level API to control headless Chrome over the DevTools Protocol",
   "main": "index.js",
   "repository": "github:GoogleChrome/puppeteer",