Build gh-pages with explicit .gitignore.

Rather than rebase gh-pages, we can start with master,
overwrite .gitignore, build, and commit one patch that
contains the binaries. Here is the overwrite, once it
is on master we can update the make script.

TBR=@arv

Review URL: https://github.com/google/traceur-compiler/pull/1130

Closes #1130.