Release 0.4.0

Added

• Added a lib.rs file so that Terracotta is now a library, with:
  • app module
  • assets module
  • auth module
  • errors module
  • health module
  • stats module
• Added working examples
  • full example with all features enabled
  • minimal example with only the core features enabled
  • api example suitable for building APIs

Changed

• Changed Terracotta from being a binary template into a library, with a full restructuring of the codebase
• Updated documentation

Removed

• Removed main.rs and non-library functionality (available as examples now)
• Removed the Dockerfile as this is no longer relevant