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
Isn't there a way to specify 2.1.x? This seems very restrictive, as it most likely than not also works with 2.1.0 or 2.1.2