(MAINT) Group gem dependencies

Allows us to speed up calls to bundler by specifying groups to operate on.

Gemfile

@@ -1,8 +1,11 @@
 source "https://rubygems.org"
 
-gem 'rspec'
-gem 'rspec_junit_formatter'
 gem 'pupperware',
     :git => 'https://github.com/puppetlabs/pupperware.git',
     :branch => 'master',
     :glob => 'gem/*.gemspec'
+
+group :test do
+    gem 'rspec'
+    gem 'rspec_junit_formatter'
+end

Makefile

@@ -41,7 +41,7 @@ ifeq ($(IS_LATEST),true)
 endif
 
 test: prep
-	@bundle install --path $$BUNDLE_PATH --gemfile $$GEMFILE
+	@bundle install --path $$BUNDLE_PATH --gemfile $$GEMFILE --with test
 	@bundle update
 	@PUPPET_TEST_DOCKER_IMAGE=$(NAMESPACE)/puppetdb:$(version) \
 		bundle exec --gemfile $$GEMFILE rspec spec