Better documentation

[augustohp]

We should have a documentation to end users on how to use the library. For that I think the most sensible approach is to have multiple markdown files inside a doc folder, we can use GitHub markdown rendering to use links exposed through a doc/README.md guiding the user through:

• Describe terms used in the documentation:
  • What is a proxy factory.
  • What is a proxy.
  • What is a storage*.
  • What is an identity generator.
• Using the library:
  • How to create and configure a proxy factory.
  • How to use a proxy.
• Extending the library:
  • Create your own proxy interceptor.
  • Create your own identity generator.
• Contributing.
• Quickstart.