Move development/test gems to group

Author: bryanhickerson

Gemfile

@@ -6,9 +6,12 @@ source 'https://rubygems.org'
 gemspec
 
 gem 'httparty', '~> 0.22'
-gem 'rake', '~> 13.0'
-gem 'rspec', '~> 3.0'
-gem 'rubocop', '~> 1.21'
+
+group :test, :development do
+  gem 'rake', '~> 13.0'
+  gem 'rspec', '~> 3.0'
+  gem 'rubocop', '~> 1.21'
+end
 
 group :test do
   gem 'simplecov', '~> 0.22', require: false