Fix compilation warnings (#61)

* add test matrix elixir 1.9, 1.10 and 1.11

* remove @doc attribute

* add matrix

.travis.yml

@@ -5,11 +5,22 @@ language: elixir
 notifications:
   recipients:
     - carlos@carloslage.net
-elixir:
-  - 1.5
-  - 1.6
-  - 1.7
-  - 1.8
+matrix:
+  include:
+    - elixir: 1.5
+      otp_release: 18.0
+    - elixir: 1.6
+      otp_release: 19.0
+    - elixir: 1.7
+      otp_release: 19.0
+    - elixir: 1.8
+      otp_release: 20.0
+    - elixir: 1.9
+      otp_release: 20.0
+    - elixir: 1.10
+      otp_release: 21.0
+    - elixir: 1.11
+      otp_release: 22.0
 before_script:
   - curl -L https://codeclimate.com/downloads/test-reporter/test-reporter-latest-linux-amd64 > ./cc-test-reporter
   - chmod +x ./cc-test-reporter

lib/json/encoder/default_implementations.ex

@@ -170,9 +170,6 @@ defimpl JSON.Encoder, for: Any do
     |> JSON.Encoder.Helpers.dict_encode()
   end
 
-  @doc """
-  Fallback method
-  """
   def encode(x) do
     x
     |> Kernel.inspect()