Add Salt 2018.3 tests

Change-Id: I6c54e7d306f4f44a79e23a99ad3ceadb204ad7a8
diff --git a/.travis.yml b/.travis.yml
index b55f809..e58885b 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -17,9 +17,11 @@
   - bundle install
 
 env:
-    - PLATFORM=epcim/salt-formulas:saltstack-ubuntu-xenial-salt-2017.7 SUITE=default
-    - PLATFORM=epcim/salt-formulas:saltstack-ubuntu-xenial-salt-2016.3 SUITE=default
-#    - PLATFORM=epcim/salt-formulas:saltstack-ubuntu-bionic-salt-2017.7 SUITE=default
+    - PLATFORM=epcim/salt:saltstack-ubuntu-xenial-salt-2016.3 SUITE=default
+    - PLATFORM=epcim/salt:saltstack-ubuntu-xenial-salt-2017.7 SUITE=default
+    - PLATFORM=epcim/salt:saltstack-ubuntu-xenial-salt-2018.3 SUITE=default
+#    - PLATFORM=epcim/salt:saltstack-ubuntu-bionic-salt-2017.7 SUITE=default
+#    - PLATFORM=epcim/salt:saltstack-ubuntu-bionic-salt-2018.3 SUITE=default
 
 before_script:
   - set -o pipefail