create_pramas method for HTTP-Post Binding

Allows ease of using a HTTP-Post binding, the client call call create_params get a hash of parameters to use in the html form.
Now the caller does not have to decode and parse a URL to get the SAMLReqeust for use in the form.
XMLSecurity::RequestDocument class

Extends REXML::Document to add XML Signature functionality.
Preform Authrequest signing if settings specify request signing

New settings were added to hold XML Signature attributes
XML signature support for LogoutRequest
Request signature test cases
Update docs to demonstrate signature functionality
fixes test failure

tests were looking for extra prams at the END of the request URL.
SAMLRequest needs to be URL-encoded
Allow metadata generation to publish the cert if request signing is specified.
Setting support for assertion_consumer_service & assertion_consumer_logout_service
handle SimpleSign request

Conflicts:
	lib/onelogin/ruby-saml/authrequest.rb
	lib/onelogin/ruby-saml/settings.rb
	test/request_test.rb
add some test
Merge pull request #1 from CompendiumSoftware/signed-requests

Signed requests