Build directly out of node_modules/traceur.
Build directly out of node_modules/traceur.

We use the previous compiler from node_modules but
we were copying it into ./build based on old two-pass
self-hosting logic. Here we clean that up so we
have a better understanding of what we are really doing.

Review URL: https://api.github.com/repos/google/traceur-compiler/issues/1424

Closes #1424.

vicb/traceur-compiler,google/traceur-compiler,longze/traceur-compiler,renie/traceur-compiler,guybedford/traceur-compiler,bazaarvoice/traceur-compiler,kittens/traceur-compiler,sid0818/traceur-compiler,johnjbarton/traceur-compiler,rossberg-chromium/traceur-soundscript,google/traceur-compiler,mathiasbynens/traceur-compiler,pandoraui/traceur-compiler,pandoraui/traceur-compiler,bazaarvoice/traceur-compiler,johnjbarton/traceur-compiler,sebmck/traceur-compiler,rossberg-chromium/traceur-soundscript,vicb/traceur-compiler,sid0818/traceur-compiler,kittens/traceur-compiler,sebgod/traceur-compiler,arv/traceur-compiler,renie/traceur-compiler,bjlxj2008/traceur-compiler,lintangarief/traceur-compiler,lintangarief/traceur-compiler,wilsonokibe/traceur-compiler,sebgod/traceur-compiler,arv/traceur-compiler,longze/traceur-compiler,wilsonokibe/traceur-compiler,sebmck/traceur-compiler,bjlxj2008/traceur-compiler