jonkemp/gulp-useref — pull request #70 by chaizhenhua (2014-11-21 11:00:02+00:00)
Title: Add Feature: allow pass stream to each asset files before concat

hello @jonkemp, this patch allow transform assets before concat. now the syntax is like
```$.useref.assets(opts, streamForEachAssetsBeforeConcat1, streamForEachAssetsBeforeConcat2, ...)```
Now we can allow sourceMaps for assets concat in this way:
```javascript
gulp.task('html', ['scripts', 'styles'], function() {
var assets = $.useref.assets({searchPath: ['.tmp/', 'src/']},
$.sourcemaps.init({loadMaps: true, debug: true})); // for each asset file load and init sourceMap
return gulp.src('src/*.html')
.pipe(assets)
.pipe($.sourcemaps.write('.'))
.pipe(assets.restore())
.pipe($.useref())
.pipe($.revReplace())
.pipe(gulp.dest('./dist'))
});
```