Clarify uglyurls flag.

Mention more clearly that, for generating `/filename.html`, you need to
set the `uglyurls` flag to `true`.
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
```
Enable aliases from .xhtml paths

When redirecting an alias from a .xhtml path, served with default content type,
a redirect only works if the html element has a xmlns attribute.  This adds the
attribute when the alias path ends in .xhtml
avoid handling a redirect from slug to slug/

because the url lacks a trailing /, many webservers will issue a
redirect to the canonical url with trailing slash for directory index
w/index.htm(l).
Append a slash to avoid this.
Merge pull request #40 from VonC/clarify_uglyurls_flag

Clarify uglyurls flag.
Complete overhaul of the docs
Adding "fork me on github" banner
Removing extra links on homepage
Return errors when rendering
Detect missed index from front matter
Removing the use of slash

An oversight on my behalf.  The FromSlash method is used when writing
out the public file name.  There is one place where the slashes are
required which is setting the output file.  I replaced those instances
with filepath.Join which should do the right thing depending on the OS.
Formatting cleanup
Merge branch 'noahcampbell-index_reporting'
Merge pull request #41 from rozza/skipStatic

Skip Static directory if its in your content directory
Merge pull request #43 from hugoduncan/feature/allow-xhtml-aliases

Enable aliases from .xhtml paths
Merge pull request #44 from cactus/avoid-redirect-with-slugs

avoid possible redirects with non-ugly slug urls