add user similarity report

app/views/reports/similar_users.html.erb

@@ -0,0 +1,28 @@
+<div id="c-reports">
+  <div id="a-similar-users">
+    <h1>Similar Users</h1>
+
+    <% if @presenter.insufficient_data? %>
+      <p>You need at least 500 favorites before Danbooru can calculate users similar to you.</p>
+
+    <% elsif @presenter.not_ready? %>
+      <p>The report is still being generated. Check back in a few minutes.</p>
+
+    <% else %>
+      <% @presenter.each_user do |user| %>
+        <div class="box">
+          <h2><%= link_to user.pretty_name, user_path(user) %></h2>
+          <div>
+            <% @presenter.each_favorite_for(user) do |post| %>
+              <%= PostPresenter.preview(post, :tags => "fav:#{user.name}") %>
+            <% end %>
+          </div>
+        </div>
+      <% end %>
+    <% end %>
+  </div>
+</div>
+
+<% content_for(:page_title) do %>
+  Similar Users - <%= Danbooru.config.app_name %>
+<% end %>