Fix SDWebImage target.

When ShareKit is added as a project to workspace and build target are configured using scheme not all implementation files are compiled and so available during runtime (specifically category in UIView+WebCacheOperation.h).

Steps to reproduce:
- Created workspace, added required target to application scheme.
- Shared link with image using VK.
- Saw `selector not found` exception.

Tests:
- Added `UIView+WebCacheOperation.{h,m}` to SDWebImage target.
- Cleaned, built the app.
- Shared link with image using VK.