Allow Markdown for header.image.caption

- Simplify and remove extra variables by condensing into one

_pages/about.md

@@ -2,10 +2,6 @@
 permalink: /about/
 title: "About the Theme"
 modified: 2014-08-08T20:53:07.573882-04:00
-image:
-  feature: sample-image-2.jpg
-  credit: WeGraphics
-  creditlink: http://wegraphics.net/downloads/free-ultimate-blurred-background-pack/
 ---
 
 Minimal Mistakes is responsive Jekyll theme with large featured images and solid typography. As the name implies the styling is fairly minimal to make it easier for you to build on top of.

_pages/home.md

@@ -4,7 +4,5 @@ permalink: /
 excerpt: "A minimal Jekyll theme for your blog by designer Michael Rose."
 header:
   image: unsplash-image-7.jpg
-  credit:
-    caption: Unsplash
-    url: https://unsplash.com
+  caption: "Photo credit: [**Unsplash**](https://unsplash.com)"
 ---