Traceur was a tool that compiled es6 to es5. As all browsers now support es6 out of the box, there is no need for it anymore. Also, both babel and typescript are now doing a better job at compiling down to es5/3 if you really insist on supporting ancient relics ;)
BTW, I feel that traceur is pretty much dead. the repo has not received any updates for over a year already.
Regards
Sander