Update dependencies and devDependencies / Remove deprecated utilities

* I updated dependencies and devDependencies of this project, and update expected encoding result of the test.
* [grunt.util._](http://gruntjs.com/api/grunt.util#grunt.util._) and [grunt.util.async](http://gruntjs.com/api/grunt.util#grunt.util.async) are [deprecated](http://gruntjs.com/blog/2013-11-21-grunt-0.4.2-released). So I replaced them with other solutions.