Add a GitHub key for Composer

[jonginn]

We can't deploy as Symfony pulls from GitHub and we've exceeded their rate. Add a key for GitHub so Composer can pull and deploy.

Could not fetch https://api.github.com/repos/symfony/HttpKernel/zipball/27abf3106d8bd08562070dd4e2438c279792c434, enter your GitHub credentials to go over the API rate limit
The credentials will be swapped for an OAuth token stored in /app/.composer/auth.json, your password will not be stored
To revoke access to this token you can visit https://github.com/settings/applications

[rossey]

I think it might be all packages pulled in by composer :(. We need to setup an auth token stored in the env and get viaduct to create an auth.json file on build with github-oauth

http://seld.be/notes/authentication-management-in-composer

[dave1010]

If you deploy with Bosh then you shouldn't have this issue :-)

[rossey]