Start the rework of the skiaperf home page using Polymer.

The file polydesign.md is the design for how the elements and objects whtat will go into the polymerized skiaperf home page.

This CL also contains the first step, creating and using the <highlightbar-sk> element.

BUG=skia:

Review URL: https://codereview.chromium.org/703773003
webtry: Update it to use metadata package.

Makes code more robust, easier to read and less spaguetti.

BUG=None
TEST=go build webtry.go && ./webtry -use_metadata=false
R=humper@google.com

Review URL: https://codereview.chromium.org/691243002