Add Salt 2018.3 tests

Change-Id: I7b740425186f02df5452120b759cab9eb4cb57fb
diff --git a/.travis.yml b/.travis.yml
index 5119179..34ac9f5 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -17,12 +17,16 @@
   - bundle install
 
 env:
-  - PLATFORM=epcim/salt-formulas:saltstack-ubuntu-xenial-salt-2016.3 SUITE=cluster
-  - PLATFORM=epcim/salt-formulas:saltstack-ubuntu-xenial-salt-2016.3 SUITE=single
-  - PLATFORM=epcim/salt-formulas:saltstack-ubuntu-xenial-salt-2017.7 SUITE=cluster
-  - PLATFORM=epcim/salt-formulas:saltstack-ubuntu-xenial-salt-2017.7 SUITE=single
-  # - PLATFORM=epcim/salt-formulas:saltstack-ubuntu-bionic-salt-2017.7 SUITE=cluster
-  # - PLATFORM=epcim/salt-formulas:saltstack-ubuntu-bionic-salt-2017.7 SUITE=single
+  - PLATFORM=epcim/salt:saltstack-ubuntu-xenial-salt-2016.3 SUITE=cluster
+  - PLATFORM=epcim/salt:saltstack-ubuntu-xenial-salt-2016.3 SUITE=single
+  - PLATFORM=epcim/salt:saltstack-ubuntu-xenial-salt-2017.7 SUITE=cluster
+  - PLATFORM=epcim/salt:saltstack-ubuntu-xenial-salt-2017.7 SUITE=single
+  - PLATFORM=epcim/salt:saltstack-ubuntu-xenial-salt-2018.3 SUITE=cluster
+  - PLATFORM=epcim/salt:saltstack-ubuntu-xenial-salt-2018.3 SUITE=single
+  # - PLATFORM=epcim/salt:saltstack-ubuntu-bionic-salt-2017.7 SUITE=cluster
+  # - PLATFORM=epcim/salt:saltstack-ubuntu-bionic-salt-2017.7 SUITE=single
+  # - PLATFORM=epcim/salt:saltstack-ubuntu-bionic-salt-2018.3 SUITE=cluster
+  # - PLATFORM=epcim/salt:saltstack-ubuntu-bionic-salt-2018.3 SUITE=single
 
 before_script:
   - set -o pipefail