Added toLowerCase for vnode.tagName to support webcomponents

[Wildhoney]

I actually think this could be a bug in Chrome's implementation of Custom Elements, but I thought I'd open a PR to at least open a discussion on it. If it is indeed a Chrome issue, then of course I don't expect this to be merged — however I couldn't find a related Chrome bug.

The issue:

Whilst in most cases HTML is case insensitive, using Custom Elements v1's customElements.define it seems that custom elements are case-sensitive when using document.createElement as shown in the following Fiddle (note: requires Chrome Canary, as customElements.define won't work in Chrome yet).

By adding toLowerCase in virtual-dom's vnode.tagName the connectedCallback function is invoked as expected. Interestingly, in the Fiddle it doesn't matter how the HTML is written (rightfully so), as both <example-node /> and <EXAMPLE-NODE /> are equals, and thus work perfectly.

Thoughts?

[coveralls]

Coverage remained the same at 97.531% when pulling 1326f2f on Wildhoney:webcomponents-v1-case-sensitivity into 947ecf9 on Matt-Esch:master.

[Wildhoney]

Raised issue.