Issue 3428 : tolerance is now passed to and used in _real_to_rational via nsimplify

The issue was that `tolerance` argument wasn't being passed to `_real_to_rational` when `nsimplify` was called with `rational=True`.
Now the argument is passed down to `_real_to_rational` and is used to return appropriate results.
Ex,
Before
`nsimplify(3.33333, tolerance=0.001, rational=True)`
`333333/100000`
Now
`3333/1000`