Add carthage support by creating a standalone Xcode project

[dreampiggy]

because we don’t want to remove Example/Pods from gitignore.

Issue to fix

Fix #5

Reason

To be compatible for carthage, since this repo was built with pod lib create, it supports it by default, however, the cost is that you should add all the code in the Example/Pods, into git repo but not ignore them.

I don't want to add Example/Pods/* into the git repo, which will contains many code from third-party depedency, and it may cause unnecessary merge conflict during branch switch.

Solution

Another solution, just create a standalone Dynamic Framework Xcode project, then all thing done. We use Cartfile to manage the dependency for this Xcode project.

So, for Carthage support, I remove the pod tempalte _Pod.xcodeproj file, and create a new standalone one, just adding all the source files and the Info.plist from the original Pods project, then everything work.

Addtional consideration

Now, the SDWebImageFLPlugin.xcodeproj use Cartfile to manage its dependency. But Example/SDWebImageFLPlugin.xcworkspace use Podfile to manage its dependency. During each of release, we should both modify Podspec as well as Info.plist to update the version. When new third-party libs was introduced (But I guess it's not possible from this plugin's design). We need to sync the dependency library's version number. This is not so convient, but it's the current best solution for a both Cocoapods && Carthage compatible solution based on the https://github.com/CocoaPods/pod-template