Fix test config (#13)

* Fix nodeunit dependency installation error

* Broaden node version range in travis config

Author: arjunmehta

.travis.yml

@@ -1,12 +1,14 @@
 language: node_js
 node_js:
-  - "1"
-  - "2"
-  - "3"
   - "4"
   - "5"
   - "6"
   - "7"
+  - "8"
+  - "9"
+  - "10"
+  - "11"
+  - "12"
 branches:
   except:
     - image

package.json

@@ -47,6 +47,6 @@
     "eslint-config-standard": "7.0.1",
     "eslint-plugin-promise": "3.5.0",
     "eslint-plugin-standard": "2.1.1",
-    "nodeunit": "0.9.0"
+    "nodeunit": "0.11.3"
   }
 }