Add makefile targets bin/tracer-runtime.js and bin/traceur-runtime.min.js
Add makefile targets bin/tracer-runtime.js and bin/traceur-runtime.min.js

Also target 'concat' to build bin/traceur.js by concatenating bin/traceur-runtime.js and a compile without a runtime.
The concat target can be tested to verify separate compilation.

Review URL: https://github.com/google/traceur-compiler/pull/513

Closes #513.

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