Change broken API to the working one

[enisaras]

I have created this pull request because the pull request #10, created by @bibajz. This PR has not been active since since August of last year but all the credit still goes to him. What I changed:

1. All mentions of swapi.co has been changed to svapi.dev, the working Star Wars API
2. Since I was having a build issue on ujson version 1.3 on python3.9 I have changed the ujson version to the latest version, I have tested the change in ubuntu 20.04 and OSX Big Sur and the package and all the models work perfectly with this version of ujson. The only thing that needs to be done now is to change the mentions of swapi.co to swapi.dev in the documentation.

I believe this package useful for Star Wars fans like me and many others and should be kept maintained, so if you are no longer interested in maintaining the package I would be more than willing to take over.