Fix typo in single.html (#67)

layouts/post/single.html

@@ -1,5 +1,5 @@
 {{ define "header" }}
-   {{/* We can overide any block in the baseof file be defining it in the template */}}
+   {{/* We can override any block in the baseof file be defining it in the template */}}
   {{ partial "page-header.html" . }}
 {{ end }}