Add svg -> iconset generator

Use public MD icons github repo
move all script into update-icons.sh

Ignore util/ and update-icons.sh for bower
Rebase on opensourced repo

Use https://github.com/google/material-design-icons 24px production svgs as the base
Rebased on release 1.0.1
add build steps to readme
Merge pull request #12 from Polymer/add-generator

Rebase on opensourced icon set