Fix SSL error with ruby 2.0 and Rails4 on OSX

If you encounter this error when trying to bundle install:

Gem::RemoteFetcher::FetchError: SSL_connect returned=1 errno=0 state=SSLv3 read server certificate B: certificate verify failed

Then it probably means than you need to upgrade your rubygem version. Check the current version:

$ gem -v

You need to use at least the 2.0.3. To upgrade, just run:

$ gem update --system