I've done some minor changes to the official Facebook plugin.
I added two new expressions:
Token - gets user's access token that can be used for AJAX requests.
Email - gets user's email.
You can download plugin docs.google.com/open (click Ctrl + S to download).
To install the plugin you have to extract facebook.zip to 'your Construct 2 installation folder\exporters\html5\plugins'
I've customized it for my needs but feel free to contact me if you need any other customizations/more expressions. I'll be happy to help.