add hasView property to region

Fixes #1632

An alternative solution would be to declare `hasView` as a function and return a boolean based on whether `currentView` is set.

thoughts @marionettejs/marionette-core?
Ok im on it

On Tuesday, 15 July 2014, Sam Saccone <notifications@github.com> wrote:

> In src/marionette.region.js:
>
> > @@ -10,6 +10,9 @@ Marionette.Region = function(options) {
> >    this.options = options || {};
> >    this.el = this.getOption('el');
> >
> > +  // set `hasView` to `false` initially until a view is shown
> > +  this.hasView = false;
>
> !! is the way to go :)
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/marionettejs/backbone.marionette/pull/1646/files#r14911497>
> .
>