Add Faker::UniqueGenerator - exclude method

[mtancoigne]

This adds an "add_to_previous_results" method to UniqueGenerator, allowing to manually specify already used values, or excluded ones.

On a Rails app, I had collisions in the tests with manually defined values and the ones created by faker. I guess there are other use cases where having this feature could be useful.

I think the test speaks for itself:

def test_unique_with_already_set_values
  values = ('a'..'z').to_a + ('0'..'9').to_a
  @tester.unique.add_to_previous_results(:character, [], values)
  assert_raise(Faker::UniqueGenerator::RetryLimitExceeded) { @tester.unique.character }
end

• Rubocop
• Documentation
• New test
• Tests passing

I can change the method name if it's not understandable.

[stympy]

Perhaps this method could be renamed to exclude... that would more clearly indicate what the method does, I think.

[mtancoigne]

I changed the method name and reworded the commit...

[vbrazo]

@mtancoigne please update the docs as well. Thanks :)

[mtancoigne]

Oh, my bad :/