Support binding specified IP (#51)

Add behavior test mode. (#42)

./go-stun -b -s stun.stunprotocol.org:3478
Mapping Behavior: EndpointIndependent
Filtering Behavior: AddressAndPortDependent
Normal NAT Type: Port Restricted cone NAT

fix and check bounds reading packets (#40)

put comments into one line

Merge pull request #30 from Piasy/master

fix #26

fix readme