Remove credo and use mix format, and lint everything

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

lib/eventos_web/views/error_view.ex

@@ -19,6 +19,6 @@ defmodule EventosWeb.ErrorView do
   # In case no render clause matches or no
   # template is found, let's render it as 500
   def template_not_found(_template, assigns) do
-    render "500.html", assigns
+    render("500.html", assigns)
   end
 end