nat_traversal 0.2.1

# NAT Traversal - Change Log

## [0.2.1]
- Better interoperability with `io::Error`

## [0.2.0]
- Implemented TCP hole punching
- Replaced ip::IpAddr with std::IpAddr
- Replaced CBOR with maidsafe_utilities::serialisation

## [0.1.0]
- Richer error information
- Smarter UDP hole punch logic
- Initial TCP port mapping implementation

## [0.0.0 - 0.0.3]
- Initial implementation