Configure MATOMO from the environment

We try to be a 12factor app right? :-)

config/piwik.yml

@@ -0,0 +1,30 @@
+# Configuration:
+# 
+# disabled
+#   false if tracking tag should be shown
+# use_async
+#   Set to true if you want to use asynchronous tracking
+# url
+#   The url of your piwik instance (e.g. localhost/piwik/
+# id_site
+#   The id of your website inside Piwik
+#
+
+default: &default
+  id_site:  <%= ENV['OSEM_PIWIK_ID'] %>
+  url: <%= ENV['OSEM_PIWIK_URL'] %>
+  use_async: <%= ENV['OSEM_PIWIK_ASYNC'] || false %>
+  disabled: <%= ENV['OSEM_PIWIK_DISABLED'] || true %>
+  hostname: <%= ENV['OSEM_PIWIK_HOSTNAME'] || 'localhost' %>
+
+production:
+  piwik:
+    <<: *default
+
+development:
+  piwik:
+    <<: *default
+
+test:
+  piwik:
+    <<: *default