Update rspec mocks dependency to ~> 3.0.0

Author: thomas-holmes

rspec-activemodel-mocks.gemspec

@@ -29,7 +29,7 @@ Gem::Specification.new do |s|
 
   s.add_runtime_dependency(%q<activesupport>, [">= 3.0"])
   s.add_runtime_dependency(%q<activemodel>,   [">= 3.0"])
-  s.add_runtime_dependency(%q<rspec-mocks>,   [">= 2.99.0.beta2"])
+  s.add_runtime_dependency(%q<rspec-mocks>,   ["~> 3.0.0"])
 
   s.add_development_dependency 'rake',     '~> 10.0.0'
   s.add_development_dependency 'cucumber', '~> 1.3.5'