Use our new multi-site history endpoint for showing site history.
Include the `site_name` in the list table if we're looking at history for more than one site.
Only send the `site_ids` argument if it's present.

Otherwise, the application mis-interprets the empty value
Singular for everythign
Merge pull request #33 from humanmade/multi-site-history

Support for getting history across multiple remote sites in one go