Use the new logo and remove unused images

_config.yml

@@ -5,8 +5,8 @@ long_description: >-
   Fast, safe and secure Continuous Delivery pipelines you can set up in minutes.
   Hosted for you, or run it yourself. Powered by open source.
 
-logo: /assets/logo.png
-image: /assets/logo.png
+logo: /assets/logos/logo-512.png
+image: /assets/logos/logo-512.png
 social:
   name: Deliverybot
   links:

_includes/logo.html

@@ -1,6 +1,6 @@
 <a class="text-gray-dark text-mono" href="/" style="text-decoration: none;">
   <h3 style="font-size: 26px; margin: 0; padding: 0;">
-    <img width="28px" height="28px" src="/assets/logos/logo-head-125x125.png" style="display: inline; margin: 0; padding: 0;">
+    <img width="28px" height="28px" src="/assets/logos/logo-64.png" style="display: inline; margin: 0; padding: 0;">
     <span style="margin-left: -8px;">{{site.title}}</span>
   </h3>
 </a>

_layouts/default.html

@@ -5,7 +5,9 @@
   <meta charset="utf-8">
   <meta http-equiv="X-UA-Compatible" content="IE=edge">
   <meta name="viewport" content="width=device-width, initial-scale=1">
-  <link rel="icon" href="/assets/logo.png">
+  <link rel="icon" href="/favicon.ico" sizes="48x48">
+  <link rel="icon" href="/assets/logos/logo-256.png" type="image/png">
+  <link rel="apple-touch-icon" href="/apple-touch-icon.png">
   {%- if site.slack_app_id %}
   <meta name="slack-app-id" content="{{ site.slack_app_id }}">
   {%- endif %}