Avoid Clobbering the Config's Pepper Value

[klondikemarlen]

The original code was always overriding the "pepper" value with table_name, so it didn't matter what you set that value to in the config.
The config's "pepper" value should be respected.

[klondikemarlen]

I didn't quite think this through, I'll throw up proper solution (that doesn't fail all the tests) quite soon.

[klondikemarlen]

The config now supports setting the pepper as a Proc and evaluating it on the class. Plus now all the tests pass! 😛.

This has the advantage that you can now both disable your pepper, and make your pepper much more complex.
i.e.

# Call a custom "pepper" method defined on the class
Hashid::Rails.configure do |config|
  config.pepper = ->(klass) { klass.pepper } 
end

# Disable pepper altogether.
Hashid::Rails.configure do |config|
  config.pepper = nil
end

[cseelus]

Can this be merged? :-)