Anybody know which app/tweak I installed added this annoying 'preview' sidebar??

SOLVED: Turns out it was a Mac OS X feature all along....! In Finder, choose View from the menu bar and then Hide Preview.

See an example picture of the sidebar here: http://i.imgur.com/VHUy8H8.png

It shows up every time I open a Finder window and I can hide it but then every time I reopen another window it comes back...

I use (or used to until El Cap broke it) TotalFinder, and wondered if it came from there... I also tried Xtrafinder...

Anybody know which app/tweak I installed added this annoying 'preview' sidebar??