Change from using a WeakMap to use expando
Update CONTRIBUTING.md

Polymer/polymer#273
remove tools submodule
Merge pull request #253 from arv/less-weak-maps

Change from using a WeakMap to use expando
test: increase mocha timeout
README: event objects are wrapped now

Fixes https://github.com/Polymer/docs/issues/149
Call nodeWasAdded on all the nodes in the added tree.
Merge pull request #256 from arv/distributed-nodes-again

Call nodeWasAdded on all the nodes in the added tree.
log the exception stack if available
Merge pull request #261 from morethanreal/master

log the exception stack if available
Fix issue with syncing render nodes
Mute mutation events during rendering and template content extraction
Merge pull request #263 from arv/fix-issue-with-render-node-sync

Fix issue with syncing render nodes
Merge pull request #264 from arv/mute-mutation-events

Mute mutation events during rendering and template content extraction
don't mute during rendering
don't mute during rendering: remove test.
Inverted hasChildNodes() logic to ensure that the existance of a firstChild means there are childNodes. Added test to verify hasChildNodes() change with formatting per guidelines.
Merge pull request #265 from labriola/patch-1

Update Node.js
Allow dispatching the same event multiple times
Add work around for X-Tag issue related to relatedTarget