bump .travis to use the LTS notation

Author: dcousens

.travis.yml

@@ -1,14 +1,14 @@
 sudo: false
 language: node_js
 node_js:
-  - "8"
+  - "lts/*"
   - "9"
   - "10"
 matrix:
   include:
-    - node_js: "8"
+    - node_js: "lts/*"
       env: TEST_SUITE=standard
-    - node_js: "8"
+    - node_js: "lts/*"
       env: TEST_SUITE=coverage
 env:
   - TEST_SUITE=unit