code: function installModule(nodeModules, dep, opts, cb) {
      var where = path.join(nodeModules, '..');
  
      console.log('installing ', where, dep.resolved);
      var cmd = 'npm install ' + dep.resolved;
  
      if (opts.registry) {
          cmd += ' --registry=' + opts.registry;
      }
  
      exec(cmd, {
          cwd: where
      }, cb);
  }
docs: /* given a location of node_modules it will try and install the
  named dep into that location.
  
  Assumes npm.load() was called