Revert "Remove constraint on the pry gem version"

This reverts commit 059a0bc.

Author: andrykonchin

dynamoid.gemspec

@@ -53,7 +53,7 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'overcommit'
   # Since 0.13.0 pry is incompatible with old versions of pry-byebug.
   # We use these old versions of pry-byebug to run tests on Ruby 2.3 which new versions don't support
-  spec.add_development_dependency 'pry'
+  spec.add_development_dependency 'pry', '~> 0.12.0'
   spec.add_development_dependency 'rake'
   spec.add_development_dependency 'rspec'
   # 'rubocop', '1.12.1' # Last version compatible with Ruby 2.4