Format the codebase and check for formatted files on CI (#46)

Author: whatyouhide

.formatter.exs

@@ -0,0 +1,3 @@
+[
+  inputs: ["{mix,.formatter}.exs", "{lib,test}/**/*.{ex,exs}"]
+]

.travis.yml

@@ -7,6 +7,9 @@ notifications:
     - [email protected]
 otp_release:
   - 18.0
+script:
+  - if [[ $(elixir --version) = *"1.6"* ]]; then mix format --check-formatted; fi
+  - mix test
 after_script:
   - mix deps.get --only docs
   - MIX_ENV=docs mix inch.report