renamed walk to search, better name for what it does
removed pluggable stuff
expand no longer sorts the input (though it is probably faster that way)
renamed walk to search
fixed documentation for search
added filter method
made the class final, the whole point is not to use inheritance here
removed the new() method, you can use clone and it won't parse anyway
remove Pluggable
removed pluggable
made them proxies for the internal tree, so you can use \arc\tree methods directly on them.