Improve error page layouting. 500 page has to stay static because it's

used from nginx when Rails fails.

app/views/layouts/error.html.haml

@@ -0,0 +1,36 @@
+!!!
+%html{:lang => "en"}
+  %head
+    %meta{:content => "text/html; charset=UTF-8", "http-equiv" => "Content-Type"}/
+    %meta{:charset => "utf-8"}/
+    %title= yield :page_title
+    %meta{:content => "width=device-width,initial-scale=1", :name => "viewport"}/
+    %link{:href => "https://fonts.googleapis.com/css?family=Roboto:400", :rel => "stylesheet"}/
+    :css
+      body {
+        font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
+        background: #282c37;
+        color: #9baec8;
+        text-align: center;
+        margin: 0;
+        padding: 20px;
+      }
+
+      .dialog img {
+        display: block;
+        margin: 20px auto;
+        margin-top: 50px;
+        max-width: 600px;
+        width: 100%;
+        height: auto;
+      }
+
+      .dialog h1 {
+        font: 20px/28px -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
+        font-weight: 400;
+      }
+  %body
+    .dialog
+      %img{:alt => "Mastodon", :src => "/oops.png"}/
+      %div
+        %h1= yield :content