Don't force the latest minitest through autotest

If minitest is loaded automatically by autotest the latest version is
used.  This leaves you with no ability to use a previous version.

Since RubyGems loads its preferred minitest through Gem::TestCase we can
let the RubyGems test files take care of it.
Fix CVE-2013-4287, remove regexp backtracking

The Gem::Version regexp used backtracking to validate gem versions.
This could cause excessive CPU usage when creating Gem::Version objects
including when packaging gems. See CVE-2013-4287.txt (in this commit)
for details.

Fixes #626
Set release date in history