Fix Piwik installer naming and add tests. Closes GH-130.

Conflicts:
	src/Composer/Installers/PiwikInstaller.php
Add piwik to main installer and tests
Remove invalid and duplicate piwik test.
Add Wolf CMS installer. Closes GH-131.
Clean up for WolfCMS installer
Add support for Kirby CMS plugins
Merge pull request #133 from matthewspencer/kirby

Add support for Kirby CMS plugins