Can I delete this folder? Library -> Application Support -> iOSinstaller
I tried deleting the folder and the system was fine after that. The file wasn't created by the PopcornTime app for Mac but the iOSInstaller of PopcornTime. I tried to install the app on my iPad and the installer created that folder and all those large files.

So to answer the question: YES you can delete that folder and all the files inside it.