Fixed #31.

Implemented test Saml2Response_Validate_FalseOnReplyFromWrongIdp
Changed XML-structure in all responses in test data to have Issue as an element instead of an attribute, according to SAML2-specification.
Changed PendingAuthnRequests to also contain info about IDP
ValidateInResponseTo: Changed config lookup of AllwounsolicitedAuthnResponse to look for the IDP specified in the Issuer field instead of the first config.
Added my self to the contributors file