Get rid of the excessive Object.create opts shadowing stuff
manage 'wait' timer properly

Calculating a new 'wait' value on each poll iteration introduces
a bit of error on each pass.  Instead, calculate the start and end
times up front, and poll until we pass that boundary.

On each retry, set the 'start' back to the current Date.now value.
manage 'retries' so it does not clash with 'wait' polling

This fixes #5 by avoiding the confusion situation where every poll can
be retried, instead of every retry doing a polling phase.
whitespace
Simulate staleness instead of waiting excessively
v1.0.0