Update pry dev dep

so we can install and test with ruby-head

Author: rwstauner

mruby_engine.gemspec

@@ -52,7 +52,7 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "rake", ">= 12.0"
   spec.add_development_dependency "rake-compiler", ">= 1.2"
   spec.add_development_dependency "rspec", "~> 3.3"
-  spec.add_development_dependency "pry", "~> 0.10.0"
+  spec.add_development_dependency "pry", "~> 0.16"
   spec.add_development_dependency "pry-byebug", "~> 3.1"
   spec.add_development_dependency "benchmark-ips", "~> 2.2"
 end