Ignore .rdoc directory for tags
Add Verisign G5 CA cert and its intermediary

https://s3.amazonaws.com changed its certificate.  We did not have the
new root CA certificate (the G5 certificate) in our default certificate
list.

This caused connections to https://rubygems.org to fail for users who
did not have a full certificate list for openssl installed separately.

Now we have both the G5 certificate and its intermediary to allow
connections to succeed for users on cert.pem-less systems.

Fixes #665

Fixes #671
Add #654 to history

Issue #654 removed redundant (useless) certificates that aren't needed
to connect to https://rubygems.org.  This was committed in @22e5981.

Fixes #654
Added a test for the included certificates
Mention #673 in History

Issue #673 adds a test for S3 and rubygems.org certificates to rubygems
so we can more quickly detect when a certificate's roots change.
Only run CA tests on travis-ci

The CA tests added in #673 run locally even when I don't have internet,
which can make the tests slower.

Now they'll only run on travis-ci which can take all the time it likes,
but will give similar value.
Add proper certificates for S3

Commit @71bc866 did not add the correct certificates as show by the test
from #673.  Now we have a tool to determine the correct certificates by
automatically from a certs.pem.

This updates #665 and #671.
Remove unneeded require of rubygems/request

Issue #673 added a test for the bundled CA certificates which requires
rubygems/request, but the file is not used in the test.
Remove ca-bundle.pem

The ca-bundle.pem contains more certificates than I wish to maintain or
police for compromises.  Limiting to just the certificates needed for
rubygems.org, S3, cloudfront and fastly will be much less work and
security risk.
Set release version and date