add Vagrantfile

The only modification after `vagrant init ubuntu/trusty64` is forwarding port 3000 on the VM to 3000 on the host.

I used to have it specify the memory size of the VM to be 1GB, because I ran into an issue with not having enough memory. That was probably just for installing stuff though, so dev's shouldn't need that. If you run into that issue though, that's what you need to do!

Also I didn't have problems with this Vagrantfile, but I've had issues with other boxes where every refresh took ~10 seconds. The solution for that is to use NFS instead of Virtualbox's default file sharing mechanism. I can assist with that if it's ever an issue.