Fix for 0 length new String

[tylermorten]

This Pull Request fixes/closes #398 .

It changes the following:

• Adds the field length with the proper length of the string to the context
• Adds a test for testing the fields is set correctly.

[Razican]

Hi! thank you for the pull request! It looks good, but it seems that this has formatting issues. Could you run cargo fmt? Also, could you add a test for a string with UTF-8 (non-ASCII) characters?

[tylermorten]

Thanks!

For the UTF-8 encoding, I'm guessing you want to support the count of the characters - not the byte length, correct? It appears that when I check the length of a String in node it gives me back the character count, not the byte count. I believe that the default for std::String len() returns the byte count...perhaps chars().count() would work better for this implementation?

[Razican]

perhaps chars().count() would work better for this implementation?

I think so, yes, I saw you already implemented this, let me give it another look :)

[Razican]

Thank you for those changes! I think this is ready to be merged. We could include it in 0.8, since we have not released it yet. What do you think, @jasonwilliams, @HalidOdat?

[HalidOdat]

Looks perfect to me!

Yes. We can include this in version 0.8. :)

[jasonwilliams]

Sorry for slow response but yes it looks good!

Thanks @TylerMorton

[tylermorten]

Thank you! I'll continue to look through issues to see if there is anything else I can help on.