Merge pull request #20 from AlbertBrand/master

Don't validate the request state when InResponseTo is empty
Support KeyDescriptor without 'use' attribute #13
unit test autoloading
Support for EntitiesDescriptor element #12
Authenticate fixed only to redirect binding and config settings ignored #23
Corrected content type header
SAML protocol response cannot be sent via bindings other than HTTP POST #24
Support for EntitiesDescriptor element #12
composer.lock at latest aerialship/lightsaml
SAML protocol response cannot be sent via bindings other than HTTP POST #24
ACS SubjectConfirmationData Recipient verification #16
Assertion must be signed if HTTP POST binding is used #17
signing service not accessed correctly #22
SAML protocol response cannot be sent via bindings other than HTTP POST #24
Assertion must be signed if HTTP POST binding is used #17
Changed TwigEngine to DelegatingEngine
Merge pull request #26 from andrew-jones/master

Changed TwigEngine to DelegatingEngine
Revert "Merge pull request #26 from andrew-jones/master"

This reverts commit c1aa6ee4637349d4342537e6c854c5210e59923f, reversing
changes made to 2c10f066ccda0b626e7ee3d9f08c45c05aad215f.
Merge pull request #25 from tamlyn/patch-2

Corrected content type header in LogoutReceiveRequest
Make NameIDPolicy optional in AuthRequest  aerialship/lightsaml#22
Added metadata exchange step

I had trouble working out where to download the SP metadata from.