stop using rspec private APIs

[michaelglass]

Presently, we use private apis which could change in minor versions, lets try to do it another way.

see: https://github.com/y310/rspec-retry/blob/85754e196361f909615d11013ba2b896e517cf53/lib/rspec_ext/rspec_ext.rb and #25

[myronmarston]

In RSpec itself we don't ever clear the memoized hash...we just instantiate a new example group instance for each spec. Maybe you can use a similar strategy?

Alternately, if there's a reason that won't work for you and you want a public API for clearing the memoized values, let us know.

[JonRowe]

Creating new instances would be the way I would try to do this too...