Put database.yml into the code base

It works by default, we have a mechanism to configure it (dotenv.example)
and we want to be a 12factor app, right? Let's do this...

config/database.yml

@@ -0,0 +1,32 @@
+<%
+  encoding = 'unicode'
+  if ENV['OSEM_DB_ADAPTER'] == 'mysql2'
+    encoding = 'utf8'
+  end
+%>
+
+
+default: &default
+  adapter: <%= ENV['OSEM_DB_ADAPTER'] || 'postgresql' %>
+  encoding: <%= encoding %>
+  host: <%= ENV['OSEM_DB_HOST'] || 'database' %>
+  port: <%= ENV['OSEM_DB_PORT'] || '5432'  %>
+  username: <%= ENV['OSEM_DB_USER'] || 'postgres' %>
+  password: <%= ENV['OSEM_DB_PASSWORD'] || 'mysecretpassword' %>
+  database: <%= ENV['OSEM_DB_NAME'] || 'postgres' %>
+  pool: 5
+  timeout: 5000
+
+development:
+  <<: *default
+  database: osem_development
+
+# Warning: The database defined as "test" will be erased and
+# re-generated when you run "rake".
+# Do not set this db to the same as development or production.
+test:
+  <<: *default
+  database: osem_test
+
+production:
+  <<: *default