add inanimate option

I added :inanimate option to UIView.animate.

It's just an idea.
I think there is a more better way.

I want to move a view as rotating.
With :inanimate option, like this.
```
    animate {
      self.slide(:right, size:50, inanimate:true)
      self.rotate_to(angle:90.degrees, inanimate:true)
    }
```

But nesting is annoying and require reverse ordering.
```
    animate(after: Proc.new {
      animate(after: Proc.new {
        animate(after: Proc.new {
          animate {
            self.slide(:up, size:50, inanimate:true)
            self.rotate_to(angle:0.degrees, inanimate:true)
          }
        }) {
          self.slide(:left, size:50, inanimate:true)
          self.rotate_to(angle:270.degrees, inanimate:true)
        }
      }) {
        self.slide(:down, size:50, inanimate:true)
        self.rotate_to(angle:180.degrees, inanimate:true)
      }
    }) {
      self.slide(:right, size:50, inanimate:true)
      self.rotate_to(angle:90.degrees, inanimate:true)
    }
```

I make a sample project.
https://github.com/katsuyoshi/sugarcube-animation-test