- move the webp component + the libwebp dependency to SDWebImage/SDWebImageWebPCoder (including tests and demo)
- Xcode 9.4
- instead of directly linking the Demos to the frameworks, using CocoaPods (`Examples/Podfile`). This allows using SDWebImage/SDWebImageWebPCoder into our examples so we keep the WebP demos
- demos code cleanup and warnings resolved
- all links from docs (README, Migration guide, CHANGELOG) are full links, so they work even from external pages (i.e. https://cocoapods.org/pods/SDWebImage).
- added "Additional modules" section to README