Randomization stuff

Hi!

I was reading through minitest code and I found one place which didn't seem right: https://github.com/seattlerb/minitest/blob/master/lib/minitest/test.rb#L67. Why are we sorting the array before shuffling it? I thought that was not neccessary and removing it would save as some CPU cycles, so I removed it. Then the test suite start failing and reading through it I found this: https://github.com/seattlerb/minitest/blob/master/test/minitest/metametameta.rb#L86. I'd say the only reason both lines are there is to make the tests pass... so I've removed them if this PR.

Let me know whether all this make any sense.

Cheers!