Fix "me" image on the about page

Add a section shortcode to enable wrapping a chunk of a post in a <section>
Add a section.flow class that removes grid from the section
Fix up the about styles so that the paragraph that Hugo wraps the <img> in behaves sensibly when floated
Fix the alt text in the circular_image shortcode

layouts/shortcodes/section.html

@@ -0,0 +1,3 @@
+<section {{ with .Get "class" }}class="{{ . }}"{{ end }}>
+  {{ .Inner }}
+</section>