Add permalinks to all articles

They're not pretty (enough) yet, but kinda neat.  Maybe they should be
at the end of the article, though.  Or more to the side, so that media
posts without titles look better.

go/blog/blog.go

	},
}
var shellTmpl = template.Must(template.New("shell").
var baseTmpl = template.Must(template.New("base").
	Funcs(funcs).Parse(`
{{ define "title" }}
	<header>
		{{- if .Title }}
		<h1>{{ .Title }}</h1>{{ end }}
		<a class="permalink" href="#{{ .Id }}">∞</a>
		{{- if .Date }}
		<time>{{ .Date }}</time>{{ end }}
	</header>
{{ end }}
`))
var shellTmpl = template.Must(baseTmpl.New("shell").
	Funcs(funcs).Parse(`
<article id="{{ .Id }}" class="shell">
	<header>
</article>
`))
var linkTmpl = template.Must(template.New("link").
var linkTmpl = template.Must(baseTmpl.New("link").
	Funcs(funcs).Parse(`
<article id="{{ .Id }}" class="link">
	<header>
</article>
`))
var imageTmpl = template.Must(template.New("image").
var imageTmpl = template.Must(baseTmpl.New("image").
	Funcs(funcs).Parse(`
<article id="{{ .Id }}" class="image">
	{{- if .Title }}
	<header>
		<h1>{{ .Title }}</h1>
		<a class="permalink" href="#{{ .Id }}">∞</a>
		{{- if .Date }}<time>{{ .Date }}</time>{{ end -}}
	</header>
	{{- end }}
	{{- template "title" . }}
	<img src="{{ safe_url .URL }}" />
	{{- if .Content }}
</article>
`))
var songTmpl = template.Must(template.New("song").
var songTmpl = template.Must(baseTmpl.New("song").
	Funcs(funcs).Parse(`
<article id="{{ .Id }}" class="song">
	{{- if .Title }}
	<header>
		<h1>{{ .Title }}</h1>
		<a class="permalink" href="#{{ .Id }}">∞</a>
		{{- if .Date }}<time>{{ .Date }}</time>{{ end -}}
	</header>
	{{- end }}
	{{- template "title" . }}
	<audio src="{{ safe_url .URL }}" controls>
		Your browser can't play {{ .URL }}.
	</audio>
</article>
`))
var textTmpl = template.Must(template.New("text").
var textTmpl = template.Must(baseTmpl.New("text").
	Funcs(funcs).Parse(`
<article id="{{ .Id }}" class="text">
	<header>
		<h1>{{ .Title }}</h1>
		<a class="permalink" href="#{{ .Id }}">∞</a>
		{{- if .Date }}<time>{{ .Date }}</time>{{ end -}}
	</header>
	{{- template "title" . }}
	{{- if .Content }}
	{{ markdown .Content }}
</article>
`))
var videoTmpl = template.Must(template.New("video").
	Funcs(funcs).Parse(`
var videoTmpl = template.Must(baseTmpl.Parse(`
<article id="{{ .Id }}" class="video">
	{{- if .Title }}
	<header>
		<h1>{{ .Title }}</h1>
		<a class="permalink" href="#{{ .Id }}">∞</a>
		{{- if .Date }}<time>{{ .Date }}</time>{{ end -}}
	</header>
	{{- end }}
	{{- template "title" . }}
	<iframe width="560" height="315" src="https://www.youtube.com/embed/{{ .URL }}" frameborder="0" allowfullscreen></iframe>
	{{- if .Content }}