[COOK-4356] Gets WordPress to be extracted to the proper directory

This is specific to Linux:

In this cookbook, the attribute `node['wordpress']['dir']` is not where files are being installed, instead the tarball is being extracted to the `parent_dir` and everything is found in `parent_dir/wordpress`. Proposed solution is to add `--strip-components 1` to the tar command and change the extraction path to `node['wordpress']['dir']`. This will make sure WordPress is actually installed into the proper directory. This will also turn `node['wordpress']['parent_dir']` into an unused attribute for Linux installs.

For Windows: I didn't see an easy fix for doing this since a `strip-components` option is available w/zip.