Bugfix: When providing default value on load the validator is always null

[DavidCorrado]

Bug Report:
#9

Comments for reviewer:

• I removed all intellij files and .gitignored. This seems to be recommended. I also .gitignored some files that were auto generated in my project for iOS.
• Fixed a warning with the validator that said you must always return something. Returning null is the proper thing to return if passed validation: https://flutter.dev/docs/cookbook/forms/validation
• Made a breaking change. I removed value. Seems like its more standard to have initialValue. I essentially just replaced your value for the built in state.value. In which initialvalue automatically sets state.value as you can see in https://github.com/flutter/flutter/blob/e0c63cd35e15e407a80dc44281cc392535fcce25/packages/flutter/lib/src/widgets/form.dart#L422

I appreciate your consideration for including. Thanks for creating this library.

[alienriquebm]

This is very important. We need this fix very very soon!

[cetorres]

Thank you, @DavidCorrado!

[alienriquebm]

Thanks @DavidCorrado and also thanks to you @cetorres for this great widget. You will publish the update on pub.dev soon?

[cetorres]

@aebmknrl I just published it. Thanks.

[alienriquebm]

Thanks to you brother. Please when you have some time, check my PR. Thanks

[cetorres]

@aebmknrl your PR is with a conflict now. Can you fix it?

[alienriquebm]

Yes my friend, i will check it out in a few minutes