test elixir 1.8.1

Author: getong

.travis.yml

@@ -6,17 +6,16 @@ cache:
     - ~/.mix
     - _build
 
-elixir:
-  - 1.4
-  - 1.6
-
-otp_release:
-  - 19.3
-  - 20.0
 
 matrix:
   include:
-    - otp_release: 20.0
+    - otp_release: 21.3
+      elixir: 1.8
+    - otp_release: 21.3
+      elixir: 1.7
+    - otp_release: 20.3
+      elixir: 1.6
+    - otp_release: 19.3
       elixir: 1.5
     - otp_release: 18.3
       elixir: 1.4