* changed to run foreman with vagrant

* change port specification method and database setting

* delete changes of environment variable related code

* hard coated the port

Export environment variables from .env.vagrant before running rails commands in Vagrant provisioning (#2343)

Fix #1940

Prior to this commit, the vagrantfile installs ruby 2.3.3. Due to commit 7951e7ff, this no longer works.

Change the provision scrip so that 2.3.1 is installed via rbenv. Note this drastically increases provision time.

The current Vagrantfile fails to build upon provisioning, as it lacks yarn.

Change the Vagrantfile to add the yarn repository, and install yarn.