Adding AFNetworking architecture diagram
Fixing link to diagram in README
Fixing center alignment
Update README.md
Use NSURL methods instead of CFURL functions

* Replace CFURLCopyUserName with -[NSURL user]
* Replace CFURLCopyPassword with -[NSURL password]
Rename the `username` variable to `user`
Merge pull request #743 from 0xced/NSURL-user-password

Use NSURL methods instead of CFURL functions