Adds initial video playback support and multiple image support

[inb4ohnoes]

I've added my own multiple image support and video support based on larcus94's fork, updated for AVFoundation and other deprecations. The multiple image support has Twitter's 4 image limit in mind, but can probably be easily updated to accommodate more images.

PLEASE NOTE that this is only a jumping off point and is not meant to be merged immediately. I've only got a very rough implementation going and things are very likely to break. I'd like to get a dialogue going about possible changes to this that we can then end up integrating into master. All yours, @jaredsinclair :dancer:

[winzig]

@inb4ohnoes I was interested in these features so was checking out your branch, but can't get it to compile. Looks like JTSMediaInfo.h (replacement for JTSImageInfo.h?) is missing from the repo?

[inb4ohnoes]

Sorry about that, try it again.

[winzig]

@inb4ohnoes OK it's compiling now, thanks. However, experimenting with the sample app (modified to try and use the new functionality), it doesn't seem to be working. I've tried setting imageInfo.videoURL to an NSURL pointing to a video, instead of setting imageInfo.image, but then it crashes. (Looks like the code requires either the .image or .imagePlaceholder property to be set.) So I just set .image to the banecat image (the default), and ALSO set the videoURL, just to see if the video might start playing, but I don't see anything happening except for the image display.

Can you provide an example of how you fire it up? Thanks!

[inb4ohnoes]

I have not updated the sample project to work with the new modifications yet, mainly because I haven’t actually finished the implementation yet. When I get time this weekend I will be able to probably update the sample to work with the current implementation.