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.
no need to sort styleNodes in styleItem method since they are sorted already by setFilePath:error
Merge pull request #59 from keithnorm/keith/fix-precedence

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