修复：添加reset.css和cell加上right-icon的slot (#27)

* add reset css and remove postcss-salad

* cell add right icon slog

packages/vant-css/gulpfile.js

@@ -1,11 +1,11 @@
 var gulp = require('gulp');
 var postcss = require('gulp-postcss');
 var cssmin = require('gulp-cssmin');
-var salad = require('postcss-salad')(require('./salad.config.json'));
+var postcssPlugin = require('../../build/utils/postcss_pipe')();
 
 gulp.task('compile', function() {
   return gulp.src('./src/*.css')
-    .pipe(postcss([salad]))
+    .pipe(postcss(postcssPlugin))
     .pipe(cssmin())
     .pipe(gulp.dest('./lib'));
 });