run npm test in matrix for node 8,10,12 (#13)

diff --git a/.travis.yml b/.travis.yml
index 9bfe740..f97c220 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -17,7 +17,9 @@
 
 language: node_js
 node_js:
+  - 8
   - 10
+  - 12
 services:
   - docker
 
@@ -31,8 +33,5 @@
 before_install:
   - ./travis/scancode.sh
 
-before_script:
-  - echo "Placeholder setup script"
-
 script:
-  - echo "Placeholder testing script"
+  - npm test -- -v