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)

Not your doing (AFAIK) and probably not a blocker, but elsewhere in this PR (and throughout framework) there is code like this that tries to see if the response was a redirect and gets the Location header if so.  Each does it slightly differently (here, you look for any 3xx, but earlier you were looking for just 301-302).  I would suggest adding a helper method somewhere so people don't need to reinvent the wheel.