Clarify pac4j-saml documentation

Clarify the origin of the IDP metadata file, see discussion in ML, https://groups.google.com/forum/?hl=en#!topic/pac4j-users/voRxEm-rYho
Merge pull request #68 from olafurpg/master

Clarify pac4j-saml documentation
fix documentation on SAML
Merge pull request #69 from miremond/master

fix documentation on SAML
remove username field for Facebook client
Pull in core some constants and config options
Merge pull request #70 from miremond/pac4j-16

Pull in core some constants and config options
Use newer versions of Maven plugins
Merge pull request #72 from benmccann/mvn-upgrade

Use newer versions of Maven plugins
Added support for setting forceAuth, comparisonType, bindingUri to the Saml2Client
Added support for setting forceAuth, comparisonType, bindingUri to the Saml2Client
Code review comment fixes
Removed a TODO
Fix the GitHub OAuth tests
Merge pull request #75 from benmccann/fix-tests

Fix the GitHub OAuth tests
Few more code review comments
Removing the custom binding uri changes to ACS
update to CAS client 3.3.2 for security reasons
revert to 3.3.1: can't drop in place
Fix compilation of Twitter unit tests. Was getting 'Unresolved compilation problem' making two of the tests fail