Bumps minimum node engine to 8+ (#4474)

* Use node 8 as development environment

* fixup! Use node 8 as development environment

* bump node to 8.10

* Targets node 8 for everything

* Run npm install so lock file is up to date

* Use push adapter v3

* Deflake a test on ParseUser

* Adds slight delay after logout

* Ensure we wait even if call fails

* Use node carbon

package.json

@@ -20,7 +20,7 @@
   "license": "BSD-3-Clause",
   "dependencies": {
     "@parse/fs-files-adapter": "1.0.1",
-    "@parse/push-adapter": "2.0.3",
+    "@parse/push-adapter": "3.0.0-alpha2",
     "@parse/s3-files-adapter": "1.2.1",
     "@parse/simple-mailgun-adapter": "1.0.2",
     "bcryptjs": "2.4.3",
@@ -74,11 +74,11 @@
     "test": "cross-env MONGODB_VERSION=${MONGODB_VERSION:=3.2.6} MONGODB_STORAGE_ENGINE=mmapv1 TESTING=1 jasmine",
     "coverage": "cross-env MONGODB_VERSION=${MONGODB_VERSION:=3.2.6} MONGODB_STORAGE_ENGINE=mmapv1 TESTING=1 nyc jasmine",
     "start": "node ./bin/parse-server",
-    "prepublish": "npm run build",
+    "prepare": "npm run build",
     "postinstall": "node -p 'require(\"./postinstall.js\")()'"
   },
   "engines": {
-    "node": ">=6.11.4"
+    "node": ">= 8"
   },
   "bin": {
     "parse-server": "./bin/parse-server"