Update push hosts

shopify_api.gemspec

@@ -11,7 +11,7 @@ Gem::Specification.new do |s|
   s.email = %q{developers@jadedpixel.com}
   s.homepage = %q{http://www.shopify.com/partners/apps}
 
-  s.metadata['allowed_push_host'] = 'http://rubygems.org'
+  s.metadata['allowed_push_host'] = 'https://rubygems.org'
 
   s.extra_rdoc_files = [
     "LICENSE",