update iconset path.
make sure designed element does not get queued for registration.
Fixes #56
Update README.md

Point out metadata.html gotcha
Include paper-calculator and topeka-elements in designer.
rename canvas to designCanvas for styling reasons
Step 1 to on https://github.com/Polymer/designer/issues/65
Remove polyfill specific code that's no longer needed.
For startup iframe comm, avoid postMessage asynchrony which is problematic in IE by communicating directly
bind to _style for compat with IE
Forcing SD polyfill rendering after design change.
Close GH-72. Add advice for bower resolutions
Fixes https://github.com/Polymer/designer/issues/62
audit license headers
remove BOM
Eliminate unnecessary elements from preview
Correcting typographical errors in README.md
Merge pull request #76 from vincentsimard/master

Correcting typographical errors in README.md
Designer now warns if page is navigated away when changes are pending; if attempting to update a non-owned gist, will auto-create a new one.
Factor code editor and fixes https://github.com/Polymer/designer/issues/39.