fix(task-name): replace serve:dist by preview for clarity purpose

`preview` is easier to remind, and represents more the task purpose.
It also have the advantage to be less `generator-angular-fullstack`
oriented.

`preview` is just for testing that all is ok, so it not use the
livereload and nodemon abilities. Using `serve` term could cause
some confusions, let's bypass that.

README.md

@@ -29,7 +29,7 @@ Build `sass` files, inject all scripts and styles to the project, watch them and
 
 Wipe old generated `dist` directory while keeping the `.git` to preserve your remotes configuration. Concat all the scripts and vendors in one minified `.js` file, same thing for your styles. Rev all resources for caching purposes; copy the server part.
 
-    gulp serve:dist
+    gulp preview
 
 Run the `gulp build` process and serve the `dist` directory.
 

app/templates/gulpfile.js

@@ -208,7 +208,7 @@ gulp.task('serve', ['watch'], function () {
     });
 });
 
-gulp.task('serve:dist', ['build'], function () {
+gulp.task('preview', ['build'], function () {
   process.env.NODE_ENV = 'production';
   require('./dist/server/server');
   return gulp.src('client/index.html')