Wordpress - extracted check version to module

inspired by @jvazquez-r7 I also added some wordpress specs and applied rubocop suggestions.
Also added support for a custom wp-content directory.

See #3554 for some more rspecs

Rspec Output:
![rspec](https://cloud.githubusercontent.com/assets/105281/3659872/d65abbb0-11b1-11e4-8ae8-6c286cce365d.png)

Looks like the BODY_REGEX is not possible outside of the function because I use the wp_content_dir variable here. Any other ideas how to handle this? But i like the idea of having the regexes in a seperate variable