code: function(value) {
          if (undefined === value) {
              return this.$textarea.val();
          }
  
          if (parseInt(this.options.maxLine, 10) >= 1) {
              var valArray = value.split('\n'),
                  length = valArray.length;
              if (length > this.options.maxLine) {
                  valArray.splice(this.options.maxLine, length - this.options.maxLine);
                  value = valArray.join('\n');
              }
          }
  
          this.$textarea.val(value);
          this.renderLineNumber(0);
      }
docs: 以字符串形式获取/设置内容，超过 maxLine 会被截断
  @param {String} [value] 内容
  @return {String}