Fixes #73 Show a talks scheduled status in red!

Changed #scheduled? to !!predicate and display it in the talks#index.
What do you care what the type is as long as it has truthy/falsey value? You're not looking at the result, just using it within a conditional.

> On Sep 12, 2014, at 7:25, Miles Starkenburg <notifications@github.com> wrote:
> 
> In app/models/talk.rb:
> 
> > @@ -35,7 +35,7 @@ def self.older
> >    validates :title, :presenter, :email, :presence => true
> >  
> >    def scheduled?
> > -    self.scheduled_date
> > +    !!self.scheduled_date
> I already had a method that returns the date, I wanted a method that returned true/false when I asked it a question, I don't like methods that return nil.
> 
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