fix(docs): add v3.0.0 section to docs

Author: prescottprue

book.json

@@ -19,13 +19,17 @@
       "token": "UA-102355407-1"
     },
     "versions": {
-      "gitbookConfigURL": "https://raw.githubusercontent.com/prescottprue/react-redux-firebase/master/book.json",
+      "gitbookConfigURL": "https://storage.googleapis.com/docs.react-redux-firebase.com/book.json",
       "options": [
         {
             "value": "http://docs.react-redux-firebase.com/history/v2.0.0/",
             "text": "Version 2.0.0",
             "selected": true
         },
+        {
+          "value": "http://docs.react-redux-firebase.com/history/v3.0.0/",
+          "text": "Version 3.0.0"
+        },
         {
             "value": "http://docs.react-redux-firebase.com/history/v1.5.0/",
             "text": "Version 1.5.0"