code: function (dirPath) {
          'use strict';
          var me = this,
              env = process.env.NODE_ENV || 'development',
              mainPath, envPath, realPath,
              filesArr, len, i, fileName, mainName, envName;
          if (isStr(dirPath)) {
              dirPath = fs.realpathSync(dirPath);
              filesArr = fs.readdirSync(dirPath);
              len = filesArr.length;
              for (i = 0; i < len; i += 1) {
                  fileName = filesArr[i];
                  if (fileName.indexOf('main') === 0) {
                      mainName = fileName;
                  }
                  if (fileName.indexOf(env) === 0) {
                      envName = fileName;
                  }
                  if (mainName && envName) {
                      break;
                  }
              }
              mainPath = path.join(dirPath, mainName);
              me.init(mainPath);
              if (envName) {
                  envPath = path.join(dirPath, envName);
                  me.update(envPath);
              }
          }
  
          return me;
      }
docs: Full init config based on environment variable `NODE_ENV`. If `NODE_ENV` not available use `development` as default.
  This method looking for two files main (name started from 'main' word) and file with name started from environment (like development, staging, production)
  @param {string | object} dirPath - path to folder with configuration files, from project root