Added blur on iOS 8, removed redundant property

Instead of using `disableUserInteractionOfSuperview` one should use
`userInteractionEnabled` on the HTProgressHUD instance to let touches
through to the superview or not.

I also added use of UIVisualEffectView` to add a nice blur effect on iOS 8.

I went through the rest of the files and cleaned up floats, doubles and integers.

This is a really nice project! I love the extensibility without the whole project being massive! I read that you wont be able to maintain it in the future, maybe I would volunteer for that!