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.
Duplicate symbol CASStyleClassSeparator fixed
Mixed-up cas_needsUpdateStyling properties fixed (thx Imre)
Call the update on bar button items which added to the navigation bar after it appears in the view hieararchy (bad thing: in this case the bar items are still orphans)
textAttributes compatibility for iOS6
Treat the exact 'textAttributes' property as a text attributes property
UISlider+CASAddition deleted, because it resulted in stack overflow caused by double swizzing
Default implementation of didMoveToWindow in UISlider does nothing. Added category method that calls super to trigger styling.
Merge pull request #63 from gabbayabb/upstream

Various fixes
hacky POC for adding a style selector lookup table for improved performance