Improve README.md

[gdebrauwer]

• Add introduction to HATEOAS concept
• Improve introduction that tells how this package works
• Improve general example on how to use this package
• Document all customization options

[Joelfo]

I believe you could improve the Usage section explaining, for exampe, what are the parameters for the link method. I had to go to the Link class definition to be sure that is the route name and the route parameters. It was nice that i could see it there, because i'm still learning Laravewl and didn't think it was that intuitive by the example in the usage section. Anyway, it is just a suggestion. thank you for the amazing package!