Add One-up bundle with composer

*Important*: Run php composer.phar install.
Add One-up config

We are going to use the blue imp fronted. See the website’s repository
for more information.
Add Nelmio bundle

Run php composer.phar install.

Nelmio is a bundle to enable CORS (Cross Origin Resource Sharing),
important since the packets are coming from another domain.
Add Nelmio config