Upstream dependency update && Fix Carthage

Fix

• Upgrade the upstream dependency to 5.0.0-beta4. Fix the compile issue.
• Fix the Carthage install module name. Which should be just SDWebImagePDFCoder without any suffix.

Initial Release

Feature

• Supports built-in vector renderingfor PDF images, on iOS 11+/tvOS 11+/macOS 10.10+. All the built-in UIKit/AppKit class, support PDF vector render natively. Old firmware will fallback to bitmap representation.
• Supports decoding PDF image into bitmap representation using Core Graphics framework
• Supports specify desired PDF page number / bitmap size for single image request