added release notes for 0.6.4
added release notes for 0.6.4

git-svn-id: f1a1267e29db6ed751edc5bdb54cf7d87c16124a@825 410327ef-2207-0410-a325-f78bbcb22a5a

infininight/rspec-tmbundle,drnic/rspec-rails,patmaddox/rspec,mrkn/rspec,patmaddox/rspec2rails2,alitalia/rspec,dchelimsky/rspec-rails,dchelimsky/rspec-stories,die-antwort/rspec-tmbundle,dchelimsky/rspec,rspec/rspec.tmbundle,phinze/rspec,graaff/rspec,infininight/rspec-tmbundle,chip/rspec-tmbundle,die-antwort/rspec-tmbundle,rspec/rspec.tmbundle,dchelimsky/rspec,patmaddox/rspec,dchelimsky/rspec-stories,alitalia/rspec,weplay/rspec-rails,mcmire/rspec-rails