Custom class names

Now supports custom class names, such as:

let config = {
  include : [
    { ":last-child"   : "last" }, // specific replacement
    { "firstLastOnly" : "first-last" }, // replace all in group
    { "all"           : (pseudoClass) => pseudoClass.replace(":", "") } // function returning class name
  ]
};

Resolves #3.