Startup turns down rumored purchase offer
                                
                                
                                    (Newser) -
                                    Valued at a mere $1.3 billion in April, Groupon last night walked away from Google and its rumored purchase offer of between $5 billion and $6 billion, opting instead to remain independent, sources tell the  Chicago Tribune.  Neither Groupon nor Google would comment, but insiders say that the 2-year-old...