remove cache
update gitignore to ignore some files we moved to mockup
build: involve yeoman

use yeoman generator-gulp-webapp to build scaffolding
gulp: more flexible
update index.html

no bootstrap
get rid of livereload

well, I do not like live-reload. of course you are welcome to add
it back as your wish.
gulp: apply rev and rev-replace

before we distribute the project, we could change the assets filename
to avoid browser cache.