Minify CSS and JavaScript / Preserve license statement

* I bumped [gulp](https://github.com/gulpjs/gulp) module and gulp plugins.
* Currently the `Gulpfile.js` requires [gulp-uglify](https://github.com/terinjokes/gulp-uglify) and [gulp-minify-css](https://github.com/jonathanepollack/gulp-minify-css) but the [CSS](https://github.com/gulpjs/plugins/blob/58807fccb288718bbf2137bfe558a9e388b6e453/css/app.css) and [JS](https://github.com/gulpjs/plugins/blob/58807fccb288718bbf2137bfe558a9e388b6e453/js/app.js) files don't seem to be minified. So I fixed it by updating the filter path of [gulp-if](https://github.com/robrich/gulp-if).
* I introduced [uglify-save-license](https://github.com/shinnn/uglify-save-license) to preserve JavaScript license comments. It detects license statements properly, even if they have no directives such as `@license` and `/*!`.
* I bumped [ngInfiniteScroll](https://github.com/sroze/ngInfiniteScroll).
* I removed all the description of [Brunch](http://brunch.io/) and [Grunt](http://gruntjs.com/) from README. Now this project doesn't use both of them.
* I fixed a typo in blacklist.