Update make script to build gh-pages branch w/o rebase
Update make script to build gh-pages branch w/o rebase

TBR=@arv

(Half of this patch landed in 89407c5c62caccace33671df8db6bbaadddcbe83. Scripts commited to git to manipulate git branches... )

Review URL: https://github.com/google/traceur-compiler/pull/1131

Closes #1131.

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