Google has made it quite hard to install extensions that do not exist on the official Chrome Web Store.
You have to open up the extensions section and drag and drop CRX files on it. There are some improvements coming up in the future as Google developers have added support for drag and drop of complete folders to install new extensions.
This feature would be very helpful to developers who want to test out their under development extensions without compiling a CRX file every single time!
This feature is now available in the latest Chromium builds. Should land in Chrome channels in the coming weeks.