Multiple code blocks on same slide do not render correctly

[krisleech]

```ruby
# ...
```

some text

```haml
%h2 title
```

In the above "some text" and the haml code block are both rendered as Ruby syntax. I can see in script.vim that there is only one SyntaxInclude for the slide which spans the first to last line.

[krisleech]

It looks like buffer[:code] needs to be an array allowing multiple code blocks per slide/buffer?

[tybenz]

Nice catch. I'd been assuming one code-snippet per slide. Mostly because I try to break up slides with a lot of code. But it's totally valid to have 2 small code snippets on one slide.

Feel free to open a PR for this. If not, I'll try to get to it soon.

[tybenz]

I landed a fix for this. Seems to be working well. Let me know if you find problems with it.