Bump version
Add CONTRIBUTING.md, unset source in tests
Bump version
Rename Gif to UIImage+Gif
Move everything to specific folders

- SwiftGifDemo for the iOS demo
- SwiftGifCommon for the source files
- SwiftGifTests stays
Merge branch 're-order' into 1.2-development

* re-order:
  Move everything to specific folders
  Rename Gif to UIImage+Gif
Merge branch '1.2-development'

* 1.2-development:
  Move everything to specific folders
  Rename Gif to UIImage+Gif
  Bump version
  Add CONTRIBUTING.md, unset source in tests
  Bump version