Add .min.css version, update readme and add gulp

gulpfile.js

@@ -0,0 +1,22 @@
+var gulp = require('gulp');
+var minifyCSS = require('gulp-minify-css');
+var concatCss = require('gulp-concat-css');
+var plumber = require('gulp-plumber');
+
+gulp.task('concat-css', function () {
+  gulp.src(['./devicon.css', './devicon-colors.css'])
+  .pipe(plumber())
+  .pipe(concatCss('./devicon.min.css'))
+  .pipe(gulp.dest('./'));
+});
+
+gulp.task('minify-css', function() {
+  gulp.src('./devicon.min.css')
+  .pipe(plumber())
+  .pipe(minifyCSS())
+  .pipe(gulp.dest('./'))
+});
+
+gulp.task('default', function() {
+  //
+});