Dailymotion filter clobbers HTML

[subimage]

This seems to be an issue with lots of the filters - but DailyMotion filter specifically is clobbering HTML embeds. For instance, if you already have the HTML embed and run auto_html on it, the code tries to embed it inside the embed - breaking HTML.

I believe the default behavior should be to ignore all URLs already encased within a HTML tag.

PS: I fixed a similar issue with the image filter here https://github.com/subimage/auto_html/commit/110c62727a9cc30bcb4a11c7a58d8f462dfa58c0