ruby 2.1. failing very frequently in master

As mentioned by @vsizov, the Ruby 2.1 builds are failing in master very frequently as they are not split into smaller builds:

Actually I don't think this is a good idea to add these builds because we have lots of sporadic failings and adding whole test suite run makes that builds long

This should be a straight forward change just to split the spec and spinach builds into the same as with Ruby 2.2.

Feel free to comment on this in case there are any objections...

/cc @dzaporozhets @DouweM