First merge

`method-list` (for adding breakpoints) isn't ready yet because `core-selector`  is buggy.
The plan is to put `method-list` and `object-tree` on the right side in separate tabs. But `paper-tabs` was  not being compliant with `vulanize`, so that's not done yet.

Requires `O.o()` to work.

Thank you

<b>Update for #2:</b>
`core-selector` still needs to be rewritten and so `method-list` (for breakpoints) is kind of buggy.
Issue with `paper-tabs` got sorted out, so there are tabs on the right now.

I fixed that for the main content script.
But this one has to start as soon as it can. It needs to be there before `polymer-ready` fires.
I couldn't find a way to programmatically insert it sooner than `document_start` or at the same time as `document_start` (I couldn't find a way to detect a page reload that early).