Need to lock down sinatra and activesupport

Newer version of sinatra (2+) depend on rack 2+ which requires Ruby version >= 2.2.2
breaking the travis build on older versions of ruby
See https://travis-ci.org/iain/fake_sqs/jobs/156489863

Activesupport 5+ requires Ruby version >= 2.2.2
See https://travis-ci.org/iain/fake_sqs/jobs/156491614

fake_sqs.gemspec

@@ -18,7 +18,7 @@ Gem::Specification.new do |gem|
   gem.require_paths = ["lib"]
   gem.license       = "MIT"
 
-  gem.add_dependency "sinatra"
+  gem.add_dependency "sinatra", "~> 1"
   gem.add_dependency "builder"
 
   gem.add_development_dependency "rspec"
@@ -27,6 +27,6 @@ Gem::Specification.new do |gem|
   gem.add_development_dependency "faraday"
   gem.add_development_dependency "thin"
   gem.add_development_dependency "verbose_hash_fetch"
-  gem.add_development_dependency "activesupport"
+  gem.add_development_dependency "activesupport", "< 5"
 
 end