modernize test structure, add attributes.html test
modernize test structure, add attributes.html test
don't stomp on user defined set/getAttributes
Merge branch 'master' of https://github.com/Polymer/CustomElements

Conflicts:
	src/CustomElements.js
simplify attributeChanged support overrides
simplify mixin, enforce enumerability on installed properties
support non-enumerable properties in HTMLElement prototypes (+test)
bootstrap immediately if document.readyState === 'complete', otherwise wait for 'DOMContentLoaded' instead of 'load'
also boostrap if in 'interactive' document.readyState
install .constructor on generated prototype to reference generated constructor
Update README.md
Update README.md
buildbot.git no longer required
migrate some parser features into HTMLImports, simplify boot code, set up 2-pass upgrade-before-live registration for polymer-element
fix typos
Update source map syntax from //@ to //#
fix test title
only define import link target name once
minor grammatical improvement
fix my own typo