Use frames count instead of delay to check animated GIFs

[nbianca]

There are GIFs with multiple frames and zero delay, but also GIFs with
a single frame and positive delay. The old algorithm failed for this
kind of images.

[Nakilon]

That's what I said: #114 (comment)
No need to do assumptions about whether it's animated or not -- just give library user the number of frames.

[nbianca]

@Nakilon, I could do that as well, but it would require parsing the whole GIF image. My understanding is that this library is meant to provide meta information by "fetching as little as needed".

@sdsykes, can you please review this again? I amended my commit and forced pushed.

[sdsykes]

This looks ok!

[nbianca]

Hello @sdsykes! Did you set a date when you will cut a new version of this gem?

[SamSaffron]

@sdsykes so sorry for being a nag here, any chance you can cut a new version for the festive season?

[sdsykes]

Well, a late festive version. I just pushed 2.2.1.