http://www.omgchrome.com/windows-chrome ... ide-store/
This is an intentional move by google which claims it was done for the user's safety
some users are extremely dumb and gullible and get tricked into installing spyware extensions by website, of course, for the longest time you had to jump through several hoops to manually install an extension, but that is apparently not enough. chrome seeks to protect them from themselves (supposedly) by making it impossible to install an extension not hosted on the google app store. There is no way to reenable that without modifying the source code and making your own chrome build
I sincerely hoped that iron would make that modification (At the very least hiding it behind a flag in the about:flag page or some other advanced location) but sadly they did not.