Release 0.5.1

Features:
- Update default version of wordpress to install to 3.8
- Add `wordpress::wp_proxy_host` and `wordpress::wp_proxy_port` for proxying
plugin installation.
- Add `wordpress::wp_mulitsite` and `wordpress::wp_multisite` to enable
multisite support
- Update to work with latest 2.x puppetlabs-mysql
- Update to work with latest 1.x puppetlabs-concat
- Add rspec-system integration testing, travis testing, and autopublish

Bugfixes:
- Fix ownership during installation to reduce log output and increase
idempotency.