Update PostCSS and clean code

PostCSS 0.3 was released few days ago with source map support. With old 0.1 your Grunt plugin will broke Sass or Sublime maps.

Also I clean code:
* In Autoprefixer I find, that better to use quick search by `indexOf` and only them use slow RegExps.
* In PostCSS better to clone node rather that create new one. If you clone node, it will take origin code style (like space or not space after colon) and source map will show, that clone was created from origin declaration.
* `decl._value.trimmed` is a internal property, to take trimmed value you can use `value` getter.

BTW, I will be very happy with your PostCSS feedback as first third-part user :). I add much better docs after 0.1 release. Please, [check them](https://github.com/ai/postcss/blob/master/README.md).