Linebreaks break this feature

[martin-ueding]

I use this extension with Nikola, and it is a great help. Thank you for that!

The thing that I noticed is that it skips figures which have a caption that is wrapped over multiple lines. I had this in my Markdown source:

![Partial map of China showing my two destinations. Wǔhàn is in the south,      
Běijīng is in the north.](map-china-for-title.png)

That just rendered as an image with an alt attribute. But once I changed this to one longer line, I got a <figure> tag.

![Partial map of China showing my two destinations. Wǔhàn is in the south, Běijīng is in the north.](map-china-for-title.png)

I haven't looked into the implementation, but I guess it uses regular expressions and does not include newlines in the patterns? Or it uses a parser but works with single lines only? I would appreciate if it would work with line wrapping as I have the habit to wrap everything to 80 columns.