Better support for fenced code blocks

[pdehaan]

I'm seeing some weird behavior when trying to parse code blocks (with and without specified languages).

Here's my input

Home

The quick brown paragraph jumps over the lazy lists.

> "Hooray for block quotes!"  
> — Peter

**Bold and a bulleted list:**

- One fish
- Two fish

_Italics and an ordered list:_

1. Red fish
2. Blue fish

---

## Indented code block:

    var name = 'Princess Bubblegum';

## Generic code block (fenced):

```
var fs = require('fs');
fs.readFileSync('home.md', 'utf8');
```

## JavaScript code block (fenced):

```js
var path = require('path');
path.join(__dirname, 'home.md');
```

---

## Tables?

| Name     | Value |
|----------|-------|
| Jake     | true  |
| Finn     | true  |
| Ice King | false |

And my generated output is:

<h1>Home</h1>

<p>The quick brown paragraph jumps over the lazy lists.</p>

<blockquote><p>&quot;Hooray for block quotes!&quot;<br/>&amp;mdash; Peter</p></blockquote>

<p><strong>Bold and a bulleted list:</strong></p>

<ul><li>One fish</li><li>Two fish</li></ul>

<p><em>Italics and an ordered list:</em></p>

<ol><li>Red fish</li><li>Blue fish</li></ol>

<hr/>

<h2>Indented code block:</h2>

<pre><code>var name = &#39;Princess Bubblegum&#39;;</code></pre>

<h2>Generic code block (fenced):</h2>

<p><code>
var fs = require(&#39;fs&#39;);
fs.readFileSync(&#39;home.md&#39;, &#39;utf8&#39;);
</code></p>

<h2>JavaScript code block (fenced):</h2>

<p><code>js
var path = require(&#39;path&#39;);
path.join(__dirname, &#39;home.md&#39;);
</code></p>

<hr/>

<h2>Tables?</h2>

<table><thead><tr><th>Name</th><th>Value</th></tr></thead><tbody><tr><td>Jake</td><td>true</td></tr><tr><td>Finn</td><td>true</td></tr><tr><td>Ice King</td><td>false</td></tr></tbody></table>

It's a bit tricky to read, but you can see that the indented code blocks use <p><code> instead of <pre><code>.

[pdehaan]

You can also see that — Peter gets converted to — Peter, which doesn't seem right.

[pdehaan]

Oh, and here was my test case:

'use strict';

var fs = require('fs');

var markdown = require('markdown').markdown;

var output = markdown.toHTML(getFile('./test.md'), "Maruku");

console.log(output);

function getFile(src) {
  return fs.readFileSync(src, 'utf-8');
}

[codingisacopingstrategy]

I’m not sure the Maruku dialect actually supports fenced code blocks? From what I found on the internet, not by default anyway. Since the parser doesn’t recognise fenced code blocks it is falling back to the default behaviour defined by Gruber cf #223

[ashb]

Fenced code blocks are from Github Flavoured Markdown (and probably a few others) which has been started but needs more work in #41.

The &mdash is related to #16 - we don't currently support HTML (either tags or entities) so we escape everything.