Don't create state for the state_passer as a child
Apparently YAML serialization changed again some time between 1.9 and 2.1
Start testing on 2.0 and 2.1
Add ruby 2.0 fix to bundler
Only pass --keep-file-descriptors if we need it
2.0.0 was still version numbered weird
And 2.0 has its own serialization format too

I'm really unclear how they manage to keep coming up with variants
here.
Remove log line about state_passers dieing - einhorn will never see that happen