chore: update travis yml

Author: isaacs

.travis.yml

@@ -1,10 +1,15 @@
-# cipm currently relies on npm >5.4.0 to retrieve config
-before_install:
-  - npm i -g npm@>5.4.0
 language: node_js
-sudo: false
+
 node_js:
-  - "10"
-  - "9"
-  - "8"
-  - "6"
+  - node
+  - 12
+  - 10
+  - 8
+  - 6
+
+cache:
+  directories:
+    - $HOME/.npm
+
+notifications:
+  email: false