add support for SAML logout requests

- logout request support in bindings
- create logout request objects from xml
- support for format, service provider id and service provider
  qualifier attributes when generating xml in SAML name identifiers
  [rsaml/identifier/name.rb]
fix `reverse_merge' undefined method error
Merge pull request #1 from tlatsas/development

logout request support
Drop support for < 1.9.3, cleanup travis config and update the README.
Fix rubygems source.
Move to .ruby-version.
Attempt to fix #2 (ruby 2 and icon absence).
Merge branch 'ruby_2_iconv'