Move development dependencies into Gemfile

This is how `bundle gem` has generated new gems for a while now.

Author: nevans

Gemfile

@@ -3,4 +3,11 @@
 
 source "https://rubygems.org"
 
+gem "pry"
+gem "rake"
+gem "rspec"
+gem "yard"
+gem "webmock"
+gem "webrick"
+
 gemspec

vault.gemspec

@@ -26,11 +26,4 @@ Gem::Specification.new do |spec|
   spec.add_runtime_dependency "connection_pool",     "~> 2.4"
   spec.add_runtime_dependency "net-http-persistent", "~> 4.0", ">= 4.0.2"
 
-  spec.add_development_dependency "bundler"
-  spec.add_development_dependency "pry"
-  spec.add_development_dependency "rake"
-  spec.add_development_dependency "rspec"
-  spec.add_development_dependency "yard"
-  spec.add_development_dependency "webmock"
-  spec.add_development_dependency "webrick"
 end