tripple quotes disappear

[janwilmans]

int main()
{
int i = 0;
return i;
}

transforms into:

    int main()   
    {   
      int i = 0;  
      return i;  
    }  

So its get indented, and the triple quotes disappear. This makes editing code harder.

Also

```cpp
int main()   
{   
  int i = 0;  
  return i;  
}

comes out of the round-trip like:

int main()   
{   
  int i = 0;  
  return i;  
}

Which is correct HTML but does not get transformed back to markdown.