Added video uploading and privacy settings support

I think the code is pretty self-explanatory, but just a short explanation by files:
- `README`
   - Changed all absolute links (and some directing to forks instead of the origin) to relative ones
   - Added `Video` explanation
   - Added `Privacy` explanation
- `Privacy`
    * Written from scratch
- `Video`
    * Written from scratch
- `Feed`
    * Added privacy settings support
- `Photo`
    * Added privacy settings support
- `SimpleFacebook`
    * Added video uploading

If you have any questions i'm here :+1: