add "Save" button and "Near Note" position to CSL Preview

related to: https://github.com/zotero/zotero/issues/120
I think having this would be nice even without direct installation, we get a fair amount of confusion from people saving the entire webpage and I don't like having to copy this over into emacs every time, either. (For me personally, save is actually more useful then direct install)

But if you really don't like the save button let me know and I'll put up just the near-note position as a separate pull request.