Adding properties for title & corner radius and a bug fix for no title/no arrow

Here's what's in my changes:

1) FR - Adding support to adjust corner radius - We wanted a popover with a zero corner radius, but now it's a property that can be set. The default value is 10.0 as before.
2) Kind of a bug/documentation issue - The docs show you can hide the title by setting the  title on FPPopover to nil. The problem is that FPPopoverController title is not directly tied to the FPPopoverView title, which is what the code ultimately looks at. The current code looks at the title of the view controller you pass in initWithViewControlller, so the workaround is to set your view controller title to nil before initing FPPopover. Get and Set title will return the value from FPPopoverView.
3) Related to 2 - There's a bug in setupViews method of FPPopoverView when you have both no arrow and no title. The code still adds space for a title view. This has been fixed.

I tested the changes with the demo project and everything looked okay.