Add support for extracting IdP details from metadata xml
Removed unused variables and made xpath selectors more specific
Add class AttributeValue that fixes onelogin#117
AttributeValue is a String, but `AttributeValue#values` will return
all values for that attribute.
Fixes onelogin#112 by extracting all Attribute values into single array
Require AttributeValue class in correct place
Return attributes always in reverse-XML order
Merge pull request #122 from borgand/multiple-attribute-values

Fixes #112 and #117 in a backwards compatible manner
Merge pull request #119 from phene/idp-metadata-parser

Add support for extracting IdP details from metadata xml
Add support for IdP initiated logout (SLO)

Prior implementations of ruby-saml support SP initiated logout. This
adds support for IdP initiated logout.

The flow is, the IdP sends a Logout Request to the SP, and the SP
returns a Logout Response. These are implemented in the
Slo_Logoutrequest/SloLogoutresponse classes respectively.

I also added a SamlMessage class which contains some common code for
all the Saml Messages, both requests and responses, for example XML
validation and encoding/decoding.

I couldn't decide if I should have separate classes for IdP vs SP
logout, but kept them in their own classes for now. I'm happy to look
at combining them with the existing logoutrequest/logoutresponse
classes if that is deemed more appropriate.
Update test data to generic fields
LF
Add an additional assertion to valid test
Fix test for 1.8.7
Merge with upstream
Merge branch 'feature/slo' of https://github.com/buffym/ruby-saml into feature/slo

Conflicts:
	lib/ruby-saml.rb
	test/test_helper.rb