code: function inlineCSS(file, content, options, buildInfo) {
          var reg = /@import\s*url\(\s*['"]?([^\)]+?)(\?__inline)?['"]?\s*\)\s*[;]*/ig;
          var dir = path.dirname(file.path);
          return content.replace(reg, function(s, p, i){
              //相对于css构建目标目录
              var filepath = path.resolve(dir, p);
              if(!fs.existsSync(filepath)){
                  gutil.log(gutil.colors.cyan('warning:'), gutil.colors.red(pluginName + ": the file " + filepath + " is not exists"));
                  return;
              }
  
              var csscontent = fs.readFileSync(filepath, 'utf-8');
              //处理其中的url
              csscontent = replaceCSSUrl(csscontent, options, buildInfo, file.path);
              //gutil.log(gutil.colors.blue('inlineCSS:'), gutil.colors.green(filepath));
              return csscontent;
          });
      }
docs: 处理内联的css