Configure MATOMO from the environment

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

config/piwik.yml.example

@@ -1,33 +0,0 @@
-# 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
-#
-production:
-  piwik:
-    id_site: 1
-    url: localhost
-    use_async: false
-    disabled: false
-
-development:
-  piwik:
-    id_site: 1
-    url: localhost
-    disabled: true
-    use_async: false
-    hostname: localhost
-
-test:
-  piwik:
-    id_site: 1
-    url: localhost
-    disabled: true
-    use_async: false
-    hostname: localhost