Skip Static directory if its in your content directory

Allows organisation where all source files are in one directory:

```
`config.yaml`:

contentdir: "source"
staticdir: "source/static"
...

 .
	└── source
		├── post
		|	├── firstpost.md	// <- http://site.com/post/firstpost.html
		|	└── secondpost.md	// <- http://site.com/post/secondpost.html
		└── static
			└── css
				 └── site.css	// <- http://site.com/css/site.css
```