docs: function getRelativePath(cssPath, importCssPath, imgPath) {
          var count1 = 0,
              count2 = 0,
              result = '';
          importCssPath = getFilePath(cssPath, importCssPath);
          imgPath = getFilePath(importCssPath, imgPath);
          for (var i = 0, length = cssPath.length; i < length; i++) {
              if (cssPath[i] == imgPath[i]) {
                  count1++;
              } else {
                  break;
              }
          }
          count2 = cssPath.length - count1 - 1;
          for (var i = 0; i < count2; i++) {
              result += '../';
          }
          result = result + imgPath.splice(count1).join('/');
          return result;
      }