pre code tags does not include background color

[jedipunkz]

pre code tags does not include background color

[jedipunkz]

I noticed that back-quoted tag is ok, but 'space * 4 times' tag is not good.

I tested to write sample markdown.

```ruby
def test(test)
    puts test
end
```
    def test(test)
        puts test
    end

All of my contents include 'space * 8 times' tags. So do you have any ideas ?... (´・ω・｀)