Support JASIG style extra attributes

[pencil]

Some CAS server (like the JASIG's CAS Server, CASino, …) format the extra attributes a bit different. Example:

<cas:serviceResponse xmlns:cas='http://www.yale.edu/tp/cas'>
  <cas:authenticationSuccess>
    <cas:user>psegel</cas:user>
    <cas:attributes>
      <cas:employeeid>54</cas:employeeid>
      <cas:first_name>P. Segel</cas:first_name>
      <!-- ... -->
    </cas:attributes>
  </cas:authenticationSuccess>
</cas:serviceResponse>

Links:

• https://issues.jasig.org/browse/CAS-738
• https://pypi.python.org/pypi/django-cas-provider/0.3.1 (CUSTOM USER ATTRIBUTES FORMAT)
• https://github.com/biola/rack-cas/blob/master/lib/rack-cas/service_validation_response.rb#L36

[pencil]

Would be awesome if you could merge this and release a new version of the gem :+1:

[dlindahl]

I don't really have the time to verify these changes so I'm just going to take your word for it :stuck_out_tongue: