Added call to donate after npm install

Author: xdamman

package.json

@@ -29,6 +29,7 @@
     "mime": "1.3.4",
     "mongodb": "2.2.26",
     "multer": "1.3.0",
+    "opencollective": "^1.0.3",
     "parse": "1.9.2",
     "parse-server-fs-adapter": "1.0.1",
     "parse-server-push-adapter": "1.3.0",
@@ -75,7 +76,8 @@
     "coverage": "cross-env COVERAGE_OPTION='./node_modules/.bin/nyc' npm test",
     "coverage:win": "cross-env MONGODB_VERSION=${MONGODB_VERSION:=3.2.6} MONGODB_STORAGE_ENGINE=mmapv1 NODE_ENV=test TESTING=1 node ./node_modules/.bin/nyc ./node_modules/jasmine/bin/jasmine.js",
     "start": "node ./bin/parse-server",
-    "prepublish": "npm run build"
+    "prepublish": "npm run build",
+    "postinstall": "opencollective postinstall"
   },
   "engines": {
     "node": ">=4.6"
@@ -86,5 +88,10 @@
   "optionalDependencies": {
     "bcrypt": "1.0.2",
     "uws": "^0.14.0"
+  },
+  "collective": {
+    "type": "opencollective",
+    "url": "https://opencollective.com/parse-server",
+    "logo": "https://opencollective.com/parse-server/logo.txt?reverse=true&variant=binary"
   }
-}
+}