Parsing GFM code blocks in list is broken for Objective-C due to dashes

[Mattieuga]

If you add an objective-c code block in a list using GFM, the parsers seems to interpret the - in front of the objective-c function declaration as a new list item.

With a random JavaScript code snippet this works fine

> marked("This is a list\n1. Some first item\n2. Some second item\n```js\nvar a = 'a string';\n```\n3. Some third item")

'<p>This is a list</p>\n<ol>\n<li>Some first item</li>\n<li>Some second item<pre><code class="lang-js">var a = &#39;a string&#39;;\n</code></pre>\n</li>\n<li>Some third item</li>\n</ol>\n'

Now if add a dash in the beginning of the code snippet we'll see the misinterpretation:

> marked("This is a list\n1. Some first item\n2. Some second item\n```objc\n- (BOOL)someFun { ... }\n```\n3. Some third item")

'<p>This is a list</p>\n<ol>\n<li>Some first item</li>\n<li>Some second item\n```objc</li>\n<li>(BOOL)someFun { ... }\n```</li>\n<li>Some third item</li>\n</ol>\n'

[joshbruce]

#983

[Feder1co5oave]

Indent the content inside a list item:

$ bin/marked 
This is a list
1. Some first item
2. Some second item
    ```objc
    - (BOOL)someFun { ... }
    ``` 
3. Some third item

<p>This is a list</p>
<ol>
<li>Some first item</li>
<li>Some second item<pre><code class="lang-objc"> - (BOOL)someFun { ... }
</code></pre>
</li>
<li>Some third item</li>
</ol>