Gemfile: use https
diff --git a/Gemfile b/Gemfile
index a01bb93..35325ef 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,4 +1,4 @@
 # Use `bundle install` in order to install these gems
 # Use `bundle exec rake` in order to run the specs using the bundle
-source "http://rubygems.org"
+source "https://rubygems.org"
 gemspec