Converts float types to CGFloat

By having the private declaration of the showProgress methods as "float" and the public declaration of the showProgress methods as CGFloat, a compile targeting a 64bit architecture was failing. The progress property is a CGFloat, so I thought it made sense to convert the parameters to CGFloat.

I've also updated methods that are requesting CGFloat values but casting them to a float. 

These are issues because on a 64bit architecture, a CGFloat is a double, and not a float.