* support rendering into a shadow root
* only lowercase the first letter of an event when camel style is used
* Don't use let. Allow ShadowRoot in jshint.
* for backwards compat, lowercase the entire event when using camel style
* define a custom elements's import as a dependency when it is used in a template
* when rendering on the server, generate a script tag to assign custom-element properties.
* assign attributes to custom-element as properties when actualizing/morphing
* add basic test for rendering a custom-element and assigning properties
* use flag to mark custom elements
* fix brittle version test
c96eca1c70