Allow using latest Rake

Author: David Rodríguez

rspec-rails.gemspec

@@ -36,7 +36,7 @@ Gem::Specification.new do |s|
     end
   end
 
-  s.add_development_dependency 'rake',     '~> 10.0.0'
+  s.add_development_dependency 'rake',     '~> 10.0'
   s.add_development_dependency 'cucumber', '~> 1.3.5'
   s.add_development_dependency 'aruba',    '~> 0.5.4'
   s.add_development_dependency 'ammeter',  '1.1.2'