Make library compatible with AFNetworking 3.x.x

[Ch1llb4y]

I am already using AFNetworking 3.0 and I cannot install this pod because it requires the older version 2.0.

[JRG-Developer]

If you'd like to create a pull request for this, I'd be happy to review, provide advice, and get it merged.

Otherwise, I'm not super focused on this library right now, which unfortunately means I can't make it high priority. :/

I'll eventually get to this, but I don't know when honestly? I'm now using Alamofire for my networking needs.

[JRG-Developer]

@AnthonyMDev, again if you care about this, go for it? I'm happy to review stuff, but I'm not actively using this... are you?

[AnthonyMDev]

@JRG-Developer I've also migrated to Alamofire. I have not used this in quite a while now.

[Ch1llb4y]

Well I thought about dropping SDWebImage and stick to only AFNetworking/Alamofire(in pure Swift projects) but I need those extensive caching policies and customization capabilites of SDWebImage...
Still gonna do this pull request as those were just a few lines.