Uniform deployment process + migration to new server

I just migrated the blog to the new Digital Ocean machine I just created
No one should notice the migration at all (if you did, something went wrong)

I also finished setting up a more unified deployment process for all of our apps, and this PR is the result of applying that process to our blog, using the new server

A summary of the changes:
* nginx config included in the repo
* uses foreman and .env in production
* uses postgresql in all environments

I also set up semaphore, which will be deployment automatically once this gets merged
no. at least not for now. and if we do use it, it will be for monitoring only, not to force restarts during deployment