How do I use this with the usemin task?

[andreizilla]

Can someone please tell me how to use grunt-newer with the usemin task? This is what my Gruntfile has:

213     // Reads HTML for usemin blocks to enable smart builds that automatically
214     // concat, minify and revision files. Creates configurations in memory so
215     // additional tasks can operate on them
216     useminPrepare: {
217       html: '<%= yeoman.app %>/index.html',
218       options: {
219         dest: 'www',
220         flow: {
221           html: {
222             steps: {
223               js: ['concat', 'uglifyjs'],
224               css: ['cssmin']
225             },
226             post: {}
227           }
228         }
229       }
230     },
231 
232     // Performs rewrites based on the useminPrepare configuration
233     usemin: {
234       html: ['www/**/*.html'],
235       css: ['www/<%= yeoman.styles %>/**/*.css'],
236       options: {
237         assetsDirs: ['www']
238       }
239     },

Thanks