fixes #56 sort style nodes in ascending precedence order before applying rules.

This is to be more in line with CSS rules such that given this scenario:

UILabel {
  text-color: blue;
}

UILabel {
  text-color: red;
}

A UILabel should have red text.

Also, this missing Ball.png was breaking the example app. It's not used but I added it anyway as a quick fix.

NOTE: This is a fundamental change to Classy's behavior and may cause some stylesheets to appear to be broken if they were written in a way that relies on applying the rules from the bottom to the top of a stylesheet.