Release 0.8.0

Features:
- Add `servername` parameter to `apache` class
- Add `proxy_set` parameter to `apache::balancer` define

Bugfixes:
- Fix ordering for multiple `apache::balancer` clusters
- Fix symlinking for sites-available on Debian-based OSs
- Fix dependency ordering for recursive confdir management
- Fix `apache::mod::*` to notify the service on config change
- Documentation updates
Merge pull request #255 from hunner/release_0.8.0

Release 0.8.0
Use a more specific match for changing to worker

httpd from centos.alt.ru has both #HTTPD=/usr/sbin/httpd.worker and
confused
Add Serverspec matchers
Disable selinux first
Add system tests for prefork / worker mpm module
Correct cgi/cgid loading on worker/prefork
Merge pull request #263 from hunner/worker_multiple_matches

Use a more specific match for changing worker/prefork