Update .travis.yml and .kitchen.yml files

Change-Id: I078d0a6808b8748474aba246f3af717c925291b7
diff --git a/.kitchen.yml b/.kitchen.yml
index a12d27d..8a6a314 100644
--- a/.kitchen.yml
+++ b/.kitchen.yml
@@ -33,9 +33,9 @@
   sudo: true
 
 platforms:
-  - name: ubuntu-xenial
+  - name: <%=ENV['PLATFORM'] || 'ubuntu-xenial'%>
     driver_config:
-      image: trevorj/salty-whales:xenial
+      image: <%=ENV['PLATFORM'] || 'trevorj/salty-whales:xenial'%>
       platform: ubuntu
 
 suites: