Add support for text posts

go/blog/blog.go

			err = imageTmpl.Execute(os.Stdout, post)
		case "song":
			err = songTmpl.Execute(os.Stdout, post)
		case "text":
			err = textTmpl.Execute(os.Stdout, post)
		default:
			fmt.Fprintf(os.Stderr, "Error: no output for type '%s'\n", post.Type)
			os.Exit(1)
</article>
`))
var textTmpl = template.Must(template.New("text").
	Funcs(funcs).Parse(`
<article id="{{ .Id }}" class="text">
	<header>
		<h1>{{ .Title }}</h1>
		{{- if .Date }}<time>{{ .Date }}</time>{{ end -}}
	</header>
	{{- if .Content }}
	{{ markdown .Content }}
	{{- end -}}
</article>
`))
func exit(err error) {
	fmt.Fprintf(os.Stderr, "Error: %s\n", err)
	os.Exit(1)

go/blog/blog.yaml

  content: Shook, by [DRALMS](https://dralms.bandcamp.com/).
  date: "2016-09-25"
  type: song
- title: Introduction
  content: |
    `blog` is a tiny tool that generates your (link)blog.
    It takes a [YAML](https://yaml.org) file as input, and produces
    a single HTML file on stdout, which you could then upload to your
    server, place on your Desktop, or pass along to friends.
    `blog` is not meant to be a feature-rich program.  It does the
    bare minimum necessary to host a blog with different post types,
    and not more.  Whichever additional features you need you can
    add to your version of it.
    ## How to use it
    All posts are written in a single file `blog.yaml`, which contains
    a list of entries.
    The most basic post type is `text`, written as follows:
        - title: An example post
          content: You can use *Markdown* here...
    Optionally you can specify a `date` field.
    There are a few other types of posts:
    * `shell`, similar to text, but `title` is a shell command
    * `link`, with an additional `url` field
    * `image`, where `url` is the source of an image
    * `song`, where `url` is the source of the song
    With the exception of the `shell` type, `title` and `content`
    are optional.
  date: "2016-09-25"
  type: text