Update supported Elixir versions and only run Dialyzer for current El…

…ixir version

.travis.yml

@@ -1,29 +1,26 @@
 language: elixir
 sudo: false
 elixir:
-  - 1.3.4
-  - 1.4.5
-  - 1.5.3
-  - 1.6.4
+  - 1.5
+  - 1.6
+  - 1.7
+  - 1.8
 otp_release:
-  - 18.3
   - 19.3
   - 20.3
+  - 21.0
 matrix:
-  exclude:
-    - elixir: 1.4.5
-      otp_release: 18.3
-    - elixir: 1.6.4
-      otp_release: 18.3
-    - elixir: 1.3.4
-      otp_release: 20.3
+  include:
+    - elixir: 1.8
+      otp_release: 21.0
+      env: DIALZYER_TASK="dialyzer --halt-exit-status,"
 env:
   global:
     - MIX_ENV=test
 before_install:
   - git submodule update --init --recursive
 script:
-  - "mix do deps.get, deps.compile, compile --warnings-as-errors, dialyzer --halt-exit-status, coveralls.travis"
+  - "mix do deps.get, deps.compile, compile --warnings-as-errors, $DIALZYER_TASK coveralls.travis"
 notifications:
   email:
     - jonas.schmidt@gmx.com