Use equivalent_xml to verify xml-based content

[awead]

In certain cases, Fedora will add

<?xml version="1.0">

to the beginning of xml files if it is not present in the source. While this doesn't affect the validity of the xml data, it does break the checksum verification, so we have no way of knowing for sure if the migrated content is the same as the source.

Verification with the equivalent_xml gem would solve this.

[awead]

This is fixed in #26