chore: add node 11 ci job (#375)

Author: mayurkale22

.circleci/config.yml

@@ -35,11 +35,14 @@ workflows:
           filters: *release_tags
       - node10:
           filters: *release_tags
+      - node11:
+          filters: *release_tags
       - publish_npm:
           requires:
             - node6
             - node8
             - node10
+            - node11
           filters:
             branches:
               ignore: /.*/
@@ -67,6 +70,13 @@ jobs:
         environment: *test_env
       - *mongo_service
     <<: *unit_tests
+  node11:
+    docker:
+      - image: node:11
+        user: node
+        environment: *test_env
+      - *mongo_service
+    <<: *unit_tests
   publish_npm:
     docker:
       - image: node:8