Improve API.
Improve API.

* subversion/bindings/swig/ruby/svn/ra.rb (Svn::Ra::Session.open):
  Use nil for default config parameter value instead of an empty Hash.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion