use 1.6.0 and formatter

Author: mitchellhenke

.formatter.exs

@@ -0,0 +1,8 @@
+[
+  inputs: [
+    "lib/**/*.ex",
+    "config/*.exs",
+    "test/**/*.exs",
+    "mix.exs"
+  ]
+]

.travis.yml

@@ -3,7 +3,7 @@ elixir:
   - 1.3.4
   - 1.4
   - 1.5
-  - 1.6.0-rc.0
+  - 1.6.0
 otp_release:
   - 18.3
   - 19.3
@@ -12,11 +12,13 @@ otp_release:
 matrix:
   allow_failures:
     - elixir: 1.3.4
-    - elixir: 1.6.0-rc.0
+    - elixir: 1.4
+    - elixir: 1.5
 
 notifications:
   email:
     - [email protected]
 script:
   - mix test
   - mix credo
+  - mix format --dry-run --check-formatted