afterCopyCallback

example
```javascript
options: {
  targetDir: './',
  install: true,
  cleanTargetDir: false,
  verbose: true,
  cleanBowerDir: true,
  layout: 'byComponent',
  afterCopyCallback: function(options, source, destination, isFile) {
           var path = require('path');
           if (isFile) {
             var fullpath = options.cwd + path.sep + destination;
             if (path.extname(destination) === '.css') {
               var content = grunt.file.read(fullpath);
               var cssUrl = /(?:url\((.*?)(img)(.*?)\))/g ;
               content.replace(cssUrl, 'url:($1images$3)');
               grunt.file.write(fullpath, content);
             }
          }
     },
    bowerOptions: {
      forceLatest: true,
      production: false
    }
  },
```