Fix some Credo warnings

lib/chess.ex

@@ -1,4 +1,6 @@
 defmodule Chess do
+  @moduledoc false
+
   use Application
 
   # See http://elixir-lang.org/docs/stable/elixir/Application.html

lib/chess/auth.ex

@@ -105,10 +105,11 @@ defmodule Chess.Auth do
 
   @doc false
   def authenticate_user(username, password) do
-    Repo.one(
-      from u in User,
-      where: u.username == ^username
-    )
+    query = from u in User,
+            where: u.username == ^username
+
+    query
+    |> Repo.one
     |> Argon2.check_pass(password)
   end
 end

lib/chess/auth/guardian.ex

@@ -1,4 +1,6 @@
 defmodule Chess.Auth.Guardian do
+  @moduledoc false
+
   use Guardian, otp_app: :chess
 
   alias Chess.Auth

lib/chess/board.ex

@@ -1,4 +1,6 @@
 defmodule Chess.Board do
+  @moduledoc false
+
   def output(board) do
     Enum.map(0..7, fn (rank) ->
       Enum.map(0..7, fn (file) ->

lib/chess/store/game.ex

@@ -1,4 +1,6 @@
 defmodule Chess.Store.Game do
+  @moduledoc false
+
   use Ecto.Schema
   use Timex.Ecto.Timestamps
 

lib/chess_web/controllers/game_controller.ex

@@ -5,10 +5,12 @@ defmodule ChessWeb.GameController do
 
   def index(conn, _params) do
     changeset = Game.changeset(%Game{})
-    games = Game
-            |> Game.for_user(current_user(conn))
-            |> Game.ordered
-            |> Repo.all
+    games =
+      Game
+      |> Game.for_user(current_user(conn))
+      |> Game.ordered
+      |> Repo.all
+
     render(conn, "index.html", games: games, changeset: changeset)
   end