Added test steps for other major node versions

addresses https://www.pivotaltracker.com/story/show/152685778

.travis.yml

@@ -24,7 +24,16 @@ matrix:
   include:
     - env:
       - USE_SAUCE=false
-      - TEST_COMMAND="bash travis-node-script.sh"
+      - TEST_COMMAND="bash travis-node-script.sh v0.12.18"
+    - env:
+      - USE_SAUCE=false
+      - TEST_COMMAND="bash travis-node-script.sh v4"
+    - env:
+      - USE_SAUCE=false
+      - TEST_COMMAND="bash travis-node-script.sh v8"
+    - env:
+      - USE_SAUCE=false
+      - TEST_COMMAND="bash travis-node-script.sh v9"
     - env:
       - JASMINE_BROWSER="safari"
       - SAUCE_OS="OS X 10.11"

travis-node-script.sh

@@ -4,7 +4,7 @@ rm -rf ~/.nvm
 git clone https://github.com/creationix/nvm.git ~/.nvm
 (cd ~/.nvm && git checkout `git describe --abbrev=0 --tags`)
 source ~/.nvm/nvm.sh
-nvm install v0.12.18
+nvm install ${1:-"v0.12.18"}
 
 npm install
 npm test