Initial release

Added

• Initial release
• Reader class with get(), get_with_prefix_length(), metadata(), close(), and closed() methods
• Metadata class with all standard MaxMind DB metadata attributes
• Support for MODE_AUTO, MODE_MEMORY, and MODE_MMAP modes
• Iterator support via each method (Enumerable interface)
  • Iterate over all networks in database
  • Network-scoped iteration with optional CIDR parameter (String or IPAddr)
• InvalidDatabaseError exception for corrupt databases
• Thread-safe implementation using Rust Arc and RwLock
• Support for both String and IPAddr IP address inputs
• High-performance Rust implementation using maxminddb crate
• Comprehensive API documentation

Not Implemented

• MODE_FILE support (use MODE_MMAP instead)
• File descriptor support in constructor