update Piwik to version 2.16 (fixes #91)

www/analytics/vendor/piwik/referrer-spam-blacklist/CONTRIBUTING.md

@@ -0,0 +1,13 @@
+# Contributing
+
+To add a new referrer spammer to the list, [click here to edit the spammers.txt file](https://github.com/piwik/referrer-spam-blacklist/edit/master/spammers.txt) and create a pull request. Alternatively you can create a [new issue](https://github.com/piwik/referrer-spam-blacklist/issues/new).
+
+If you open a pull request, please:
+
+- **add one new domain per pull request**
+- explain where the referrer domain appeared and why you think it is a spammer
+- name the pull request in the format `Add xxx.yyy` so that it's easy to manage duplicates (for example `Add cyber-monday.ga`)
+- keep the list ordered alphabetically
+- use [Linux line endings](http://en.wikipedia.org/wiki/Newline)
+
+Please [search](https://github.com/piwik/referrer-spam-blacklist/issues?utf8=%E2%9C%93&q=is%3Aopen+) if somebody already reported the host before opening a new one.