code: function ( files ) {
          var me = this;
          files = files || [ ];
  
          var res = {
            changedFiles: [],
            notFoundFiles: [],
            notChangedFiles: []
          };
  
          me.normalizeEntries( files ).forEach( function ( entry ) {
            if ( entry.changed ) {
              res.changedFiles.push( entry.key );
              return;
            }
            if ( entry.notFound ) {
              res.notFoundFiles.push( entry.key );
              return;
            }
            res.notChangedFiles.push( entry.key );
          } );
          return res;
        }
docs: given an array of file paths it return and object with three arrays:
  - changedFiles: Files that changed since previous run
  - notChangedFiles: Files that haven't change
  - notFoundFiles: Files that were not found, probably deleted
  
  @param  {Array} files the files to analyze and compare to the previous seen files
  @return {[type]}       [description]