Update test suite to work with Rspec 3 and newer ruby-saml

Since the last time that this gem was messed with the ruby-saml library
has changed from Onelogin::Saml to OneLogin::RubySaml. This updates the
uses of this gem to match the new namespace. It also updates the test
suite to work with rspec 3.0's "expect" syntax. In addition to this it
pins the gem versions so that the gems updating won't break the build
for anyone who might want to contribute to this project.
Merge pull request #11 from sqm/fix-broken-test-suite

Update test suite to work with Rspec 3 and newer ruby-saml
Update code climate badge in README
Namespace elements in response according to SAML schema.
Add custom attributes_provider to encoded saml response.

In the event that a user would like to send custom attributes in the
assertion instead of the single email address attribute they can now
send in an attribute provider. This provider needs to implement a to_s
method that renders out the "AttributeStatement" element and associated
Attribute & AttributeValue elements.
Merge pull request #12 from lawrencepit/handle-custom-attributes

Handle custom AttributeStatements
Update issuer format to match Spring's SAML NameID.ENTITY that it expects the issuer to be