Reset 'let' memoization cache before running example.
Reset 'let' memoization cache before running example.

This fixes a bug where memoized objects persist inbetween retries of a
spec. This is bad for example when you assign database records in 'let'
declarations. The database transaction gets rolled back, and in a retry
you get stale records, which isn't good.

magicalbanana/pry-rescue,sethk/pry-rescue,ConradIrwin/pry-rescue