First thing you need to do it run the uninstaller (I know it looks sketchy but it's legit). I've also got a hosted copy just in case the original site goes offline.
Then you need to remove (delete) the leftover files from your system that the uninstaller does not remove.
Go to: HD/Library/LaunchAgents/
Be sure to remove the file: "com.genieoinnovation.macextension.client.plist"
Also go to: HD/Library/LaunchDaemons/
And be sure to remove the file: "com.genieoinnovation.macextension.plist"
Once those are in the trash, you'll need to click "Finder" then in the top menu bar "Go" then "Go to folder..." and type in: ~/Library/Preferences/
This should bring up your user library folder (which is normally hidden, hence the instructions above). Inside there find the file labeled "com.genieoinnovation.macextension.plist" and delete it.
Close Safari/Chrome/Firefox and reopen them. You may need to go into the individual preferences for each browser and reset the search provider to Google/Bing or whoever your favorite search engine is. After that "Install.mac" search should be gone from your system.