Move CustomElements to the latest Polymer version.

Primary changes include changes to enter/left view.

Conflicts:
	src/CustomElements.js

Merge pull request #61 from blois/enter_leave_view

Updating enterView/leaveView callbacks to apply only to primary document...
avoid using native implementation by default when document.webkitRegister is available. This is an outdated native implementation that is no longer spec compliant.

Updating enterView/leaveView callbacks to apply only to primary document.

Defer karma tests until after WebComponentsReady

Match mocha test runner timings

move MutationObserver definition to correct Firefox problem.

 - change entered/leftDocumentCallback to entered/leftViewCallback to match spec change  - update tests and make pass with native blink implementation

README: update lifecycle callback names

improve error message

Update CONTRIBUTING.md

Polymer/polymer#273
test: remove karma-ios-launcher

freshen tools

test: refactor karma conf, add safari/ios

Address same issue as PR 57. Android browser is not supported, but implemented fix since it's trivial.

Remove CustomElements.watchAllShadows. Platform repo now overrides createShadowRoot and handles this automatically. Fixes issue #24. Also fixes CustomElements build.

README: remove commmented section

Addresses https://github.com/Polymer/docs/issues/138
tweak doc generation settings

WCR must be async but use short async if available.

upgrade SideTable

fire WebComponentsReady event without delay

README: add "lifecycle" so people can easily find this section.

README: HTMLUnknownElement -> HTMLElement

Docs: remove <element> from readme

test: add karma-ie-launcher

test: add karma-ie-launcher

test: fix tests

test: add missing file

test: update grunt-karma

throw exception if `name` argument to document.register contains no dash (+test)

BUG=
R=sigmund@google.com

Review URL: https://codereview.appspot.com/13705043