* test/rubygems/test_gem_package.rb: Test for the above.
* lib/rubygems/security/policy.rb: Ensure digests are present when
verifying a gem and match the number of signatures bidirectionally.
* test/rubygems/test_gem_security_policy.rb: Test for the above.
* lib/rubygems.rb: Documentation improvements (by zzak)
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39126 b2dd03c8-39d4-4d8f-98ff-823fe69b080e