code: function verifyDependencies(pkg, blacklist) {
    var blacklisted = matchdep
      .filterAll(Object.keys(blacklist), pkg)
      .reduce(function(blacklisted, pluginName) {
        blacklisted[pluginName] = blacklist[pluginName];
        return blacklisted;
      }, {});
  
    return blacklisted;
  }
docs: Given a collection of plugin names verifies this collection against
  the blacklist. Returns an object with:
  [plugin name]=>[blacklisting reason]
  or an empty object if none of the dependencies to check are blacklisted.
  
  @param pkg - package.json contents
  @param blacklist - contents of the blacklist in JSON format