prop.selected always renders "selected" attribute

[reinux]

Very minor issue, but prop.selected should not render anything if it is false.

[dbrattli]

Could you please make a PR

[reinux]

Unless I'm missing something, it looks like this might be a little more involved than just changing the prop.selected function. The HTML selected attribute is only checked for presence, not value.

IReactProperty doesn't seem to be able to express an empty key-value pair, and it looks like the "correct" way to address this is to add a case to that, maybe called KeyOnly or something, and modify buildElement and splitProps to render a valueless property that way.

Would you be all right with that? I'm just as happy to leave it be, considering this is not a particularly important edge case beyond just the little extra time it takes to figure out what's going on initially.