Add Salt 2018.3 tests

Change-Id: Ie5d97134fb8c6b89633f99a3df670847b680c086
diff --git a/.travis.yml b/.travis.yml
index dddb039..eabffdd 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -17,9 +17,11 @@
   - bundle install
 
 env:
-    - PLATFORM=epcim/salt-formulas:saltstack-ubuntu-xenial-salt-2016.3 SUITE=keepalived-cluster
-    - PLATFORM=epcim/salt-formulas:saltstack-ubuntu-xenial-salt-2017.7 SUITE=keepalived-cluster
-#    - PLATFORM=epcim/salt-formulas:saltstack-ubuntu-bionic-salt-2017.7 SUITE=keepalived-cluster
+    - PLATFORM=epcim/salt:saltstack-ubuntu-xenial-salt-2016.3 SUITE=keepalived-cluster
+    - PLATFORM=epcim/salt:saltstack-ubuntu-xenial-salt-2017.7 SUITE=keepalived-cluster
+    - PLATFORM=epcim/salt:saltstack-ubuntu-xenial-salt-2018.3 SUITE=keepalived-cluster
+#    - PLATFORM=epcim/salt:saltstack-ubuntu-bionic-salt-2017.7 SUITE=keepalived-cluster
+#    - PLATFORM=epcim/salt:saltstack-ubuntu-bionic-salt-2018.3 SUITE=keepalived-cluster
 
 before_script:
   - set -o pipefail