allow valid kebab-case tag names

[nippur72]

following #106, react-templates currently allows to render non native HTML DOM elements (e.g. WebComponents) if they follow kebab-case naming, but due to a bug, it works only if there is only one hyphen character:

<my-tag></my-tag>         => React.createElement('my-tag', {}); // OK !
<the-my-tag></the-my-tag> => React.createElement(the - my - tag, {}); // wrong !