package.json: fetch uglify-js and es6-module-transpiler from Github over https

Git and SSH are often blocked by many proxies.

close #9

Signed-off-by: Anurag Priyam <anurag08priyam@gmail.com>
Merge pull request #11 from yeban/git_https

package.json: fetch uglify-js and es6-module-transpiler from Github over...