Polymer should allow attributes with dashes

[DartBot]

This issue was originally filed by @stevenroose

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> No dashes allowed in custom attributes
> Polymer used to recognize attributes with dashes like my-name and convert them to match properties where dashes were removed,
> and words follow the camelCase style (for example myName). This feature is no longer available. Now simply use the same name
> as the property.
>
> Because HTML attributes are case-insensitive, you can also write the name of your property entirely in lowercase. Just be
> sure that your custom-elements don’t declare two properties with the same name but different capitalization.

That's what the error messages page from Polymer.dart says (https://www.dartlang.org/polymer/reference/error-messages/).

I know that there probably was a whole discussion about this when Polymer dropped the support for dashed attributes, but I don't seem to be able to find it somewhere.

Dashes are the defacto standard for multi-word HTML tags and attributes. Not allowing them is like not allowing upper case in Java variables.

What was the reason for dropping the support? The mapping of dashed attributes to camelcase attributes sound perfectly fine for me.

[jakemac53]

duplicate of Polymer/polymer#150, I would follow it there

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Added MovedToGithub label.

[DartBot]

This issue has been moved to dart-archive/polymer-dart#336.