Merge pull request #1 from yifan-gu/master

receiver and basic test
fix(receiver.go) create a new message in handler
refactor(receiver.go) remove necessary stop channel
test(receiver_test.go) cleanup receiver after finish using it
feat(receiver.go) receiver can also send back reply
fix(receiver) fix nil check
test add sendAndReply test
Merge pull request #2 from xiangli-cmu/master

fix(receiver.go) create a new message in handler
feat(sender.go) finish a draft sender with simple test
refactor(sender.go) rename remoteAddr to raddrStr
Merge pull request #3 from xiangli-cmu/master

feat(sender.go) finish a draft sender with simple test
add a simple bench for send/receiver, small modification to send_test