Add post module to get LastSession.plist

LastSession.plist sometimes contains sensitive information such as
usernames and passwords. It'd be nice to keep this in loot.
Favor read_file instead
Delete unnecessary includes
Land #2775, @wchen-r7's post module to Safari get LastSession.plist
Make sure the file path is readable when it's ~/
There must be read_file
Land #2777, @wchen-r7's fix for safari_lastsession