Add and Refactor shortcodes.

Add the epigraph shortcode.  This should complete the Tufte-CSS
specific shortcodes.  Additionally, the section and div shortcodes
were refactored for ease of use.

README.md

@@ -7,6 +7,10 @@ attempts to be a faithful implementation of the
 It supports mathematical typesetting via [MathJax](https://www.mathjax.org).
 By utilizing copious partial templates the theme is largely customizable.
 
+## Math
+
+TODO explain the different ways to write LaTeX.
+
 ## Site Parameters
 
 The site specific parameters that this theme :wrecognizes are:
@@ -22,8 +26,7 @@ The site specific parameters that this theme :wrecognizes are:
   true, `hideDate` takes greater precedence.
 - `hideReadTime` boolean: if true, do not display the page's reading time
   estimate.  When `meta` is set to true, `hideReadTime` takes greater precedence.
-- `math` boolean: if true, try to render the page's LaTeX code using MatheJax. The
-  theme follows the conventions in [Hugo's MathJax tutorial].
+- `math` boolean: if true, try to render the page's LaTeX code using MatheJax. 
 - `meta` boolean: if true, display page meta-data author, date, categories provided
   these page parameters exist and are not overridden.  Content in the `/post` directory,
   (i.e., pages of type "post") ignore this parameter.
@@ -43,6 +46,35 @@ This theme provides the following shortcodes.
     There is nothing more beautiful than an elegant mathematical proof. 
   {{% /blockquote %}}`
   ```
+
+- `div`
+   - Description: This shortcode is provided as a work-around for wrapping
+   complex blocks of markdown in div tags. The wrapped text can
+   include other shortcodes
+   - Usage: Identical to the `section` shortcode.
+   Accepts the style parameters `class` and `id`.
+   If no only the positional argument `"end"` is passed, a closing tag
+   will be inserted.
+   - Example: `{{< div class="my-class" >}}` inserts a 
+   `<div class="my-class">` tag, while
+   `{{<div "end" >}}` inserts the closing `</div>` tag.
+
+- `epigraph`
+  - Description: Create an epigraph with the wrapped text.
+  - Usage: To include a footer with source attribution, pass in the
+  optional named parameters `pre`, `cite`, `post`. These parameters are
+  make no styling assumptions, so spacing is important.  A more compactly
+  styled epigraph will be used if the `type` parameter is set to `compact`.
+  (This just wraps the content in a paragraph tag.)
+  - Example:
+  ```html
+  {{% epigraph pre="Author Writer, " cite="Math is Fun" %}}
+  This is an example of an epigraph with some math 
+  \\(\mathbb N \subseteq \mathbb R \\)
+  to start the beginning of a section.
+  {{% /epigraph %}}
+  ```
+
 - `marginnote`
   - Description: Wrap text to produce a numberless margin note.
   - Usage: Accepts a required positional argument that is the margin note id.
@@ -51,12 +83,16 @@ This theme provides the following shortcodes.
 
 - `section`
    - Description: This shortcode is provided as a work-around for wrapping
-   complex blocks of markdown in section tags.
-   - Usage: `{{< section "<begin || end>" >}}` map respectively to
-   `<section>` and `</section>` tags.
-   - Example: `{{< section "begin" >}}` inserts a `<section>` tag, while
+   complex blocks of markdown in section tags. The wrapped text can
+   include other shortcodes
+   - Usage: Accepts the style parameters `class` and `id`.
+   If no only the positional argument `"end"` is passed, a closing tag
+   will be inserted.
+   - Example: `{{< section class="my-class" >}}` inserts a 
+   `<section class="my-class">` tag, while
    `{{<section "end" >}}` inserts the closing `</section>` tag.
 
+
 - `sidenote`
   - Description: Wrap text to produce an automatically numbered sidenote.
   - Usage: identical to `marginnote`. 

layouts/shortcodes/cite.html

@@ -0,0 +1 @@
+<cite>{{ .Inner }}</cite>

layouts/shortcodes/div.html

@@ -0,0 +1,8 @@
+{{ $loc := .Get 0  }}
+{{ if .IsNamedParams }}
+  <div {{with .Get "class"}} class="{{.}}"{{end}}{{with .Get "id"}} id="{{.}}"{{end}}>
+{{ else if or (eq $loc "") (eq $loc "begin") }}
+  <div>
+{{ else if eq $loc "end" }}
+  </div>
+{{ end }}

layouts/shortcodes/epigraph.html

@@ -0,0 +1,13 @@
+<div class="epigraph">
+<blockquote>
+{{ $t := .Get "type" }}
+{{ if eq $t "compact"  }}{{ .Inner }}{{ else }}<p>{{ .Inner }}</p>{{ end }}
+{{ if .IsNamedParams }}
+<footer>
+{{ with .Get "pre" }}{{ . }}{{ end }}
+{{ with .Get "cite" }}<cite>{{ . }}</cite>{{ end }}
+{{ with .Get "post" }}{{ . }}{{ end }}
+</footer>
+{{ end }}
+<blockquote>
+</div>

layouts/shortcodes/section.html

@@ -1,9 +1,9 @@
-{{ with .Get 0 }}
-  {{ if eq . "begin" }}
+{{ $loc := .Get 0  }}
+{{ if .IsNamedParams }}
+  <section {{with .Get "class"}} class="{{.}}"{{end}}{{with .Get "id"}} id="{{.}}"{{end}}>
+{{ else if or (eq $loc "") (eq $loc "begin") }}
   <section>
-  {{ else if eq . "end" }}
+{{ else if eq $loc "end" }}
   </section>
-  {{ end }}
 {{ end }}
     
-    

layouts/shortcodes/tag.html

@@ -0,0 +1,5 @@
+{{ if .IsNamedParams }}
+  <{{ .Get "name" }}{{with .Get "class"}} class="{{.}}"{{end}}{{with .Get "id"}} id="{{.}}"{{end}}>
+{{ else }}
+  <{{ .Get 0 }}>
+{{ end }}