remove unneeded metadata

_src/_posts/2014-03-10-just-a-normal-sunday.md

@@ -3,10 +3,7 @@ layout: photo
 title: Just a normal Sunday
 image: just-a-normal-sunday.jpg
 author: Matthias Kretschmann
-categories:
+category: photos
-- photos
-post_format:
-- Image
 ---
 
 Just a normal Sunday at Botschaft der Russischen Föderation | Embassy of the Russian Federation

_src/_posts/2014-03-15-potsdam.md

@@ -4,10 +4,7 @@ published: true
 title: Potsdam
 image: potsdam.jpg
 author: Matthias Kretschmann
-categories:
+category: photos
-- photos
-post_format:
-- Image
 ---
 
 Potsdam at Potsdamer Stadtschloss

_src/_posts/2014-03-17-typographic-diamond.md

@@ -4,10 +4,7 @@ published: true
 title: Typographic diamond
 image: typographic-diamond.jpg
 author: Matthias Kretschmann
-categories:
+category: photos
-- photos
-post_format:
-- Image
 ---
 
 Typographic diamond at Hobrechtstraße

_src/photos/index.html

@@ -7,7 +7,7 @@ category: photos
 
 <section role="main" id="main" class="row">
     
-    <h1 class="page-title icon-{{ page.category }}">{{ page.category }}</h1>
+    <h1 class="page-title icon-photos">photos</h1>
     
         <div class="masonry">
             <div class="grid-sizer"></div>