Please update to latest versions of symfony

[parljohn]

Hi, just doing a newbie install of the latest symfony versions and your composer file is on 5.0 for most packages when they've all been updated to 5.1 for a new install. Can you update this please?

[oojacoboo]

Hey @parljohn I think I tested this a few weeks ago and there were some issues. I don't recall exactly what it was now. If you'd like to fork the repo and try upgrading to 5.1 and running tests to confirm, I'd welcome a pull request on this.