Move "Page History" into button group

If the user has edit permissions, the "History" button is shown in a
button group with "Edit" and "Rename". If the user does not have edit
permissions, it's shown by itself.

This commit also renames the label from "Page History" to "History".

lib/gollum/templates/navbar.mustache

@@ -41,21 +41,19 @@
       </div>
     </div>
 
+    <div class="TableObject-item px-2">
+      <div class="BtnGroup" style="display: flex;">
         {{#history}}
-      <div class="TableObject-item pl-2 hide-sm hide-md">
           <a
-          class="btn btn-sm"
+            class="btn BtnGroup-item btn-sm hide-sm hide-md"
             href="{{history_path}}/{{escaped_url_path}}"
             id="minibutton-history"
           >
-          Page History
+            History
           </a>
-      </div>
         {{/history}}
 
         {{#allow_editing}}
-      <div class="TableObject-item px-2">
-        <div class="BtnGroup" style="display: flex;">
           {{#allow_uploads}}
             <a
               class="btn BtnGroup-item btn-sm hide-sm hide-md
@@ -80,9 +78,12 @@
               Edit
             </a>
           {{/editable}}
+        {{/allow_editing}}
       </div>
     </div>
 
+
+    {{#allow_editing}}
       {{#editable}}
         <div class="TableObject-item">
           <a class="btn btn-primary btn-sm minibutton-new-page" href="#">