Allow httparty 0.14 (#25)

This commit updates the gemspec to allow httparty 0.14

Author: gaganawhad

optimizely-sdk.gemspec

@@ -21,6 +21,6 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "rubocop", "~> 0.41.1"
 
   spec.add_runtime_dependency "murmurhash3", "~> 0.1.6"
-  spec.add_runtime_dependency "httparty", ">= 0.11.0", "< 0.14.0"
+  spec.add_runtime_dependency "httparty", "~> 0.11"
   spec.add_runtime_dependency "json-schema", "~> 2.6.2"
 end