Enhance documentation.

The goal is to improve documentation on the project. We'll do so by improving the content available in the README.

New TOC:

  - Installation
  - Basic Usage
    - What do I get?
    - How do I call an interaction?
    - What can I pass to an interaction?
    - How do I define an interaction?
    - Validation
  - Filters
    - Array
    - Boolean
    - Date
    - DateTime
    - Decimal
    - File
    - Float
    - Hash
    - Integer
    - Model
    - String
    - Symbol
    - Time
  - Advanced Usage
    - Composition
    - Documentation
    - Forms
    - Transaction
    - Translation
  - Changelog
  - Contributing
  - Credits
  - License