Drop pessimistic gem version locks

Author: David Heinemeier Hansson

jbuilder.gemspec

@@ -9,8 +9,8 @@ Gem::Specification.new do |s|
 
   s.required_ruby_version = '>= 1.9.3'
 
-  s.add_dependency 'activesupport', '>= 3.0.0', '< 5.2'
-  s.add_dependency 'multi_json',    '~> 1.2'
+  s.add_dependency 'activesupport', '>= 3.0.0'
+  s.add_dependency 'multi_json',    '=> 1.2'
 
   s.files         = `git ls-files`.split("\n")
   s.test_files    = `git ls-files -- test/*`.split("\n")