Add support for unflatten function

[Pana-g]

Closes #8

[danilofuchs]

Hi! Thanks for your PR, just got around to look at it. I will add some tests and get it merged/published!

[danilofuchs]

Hi @Pana-g!
I ported the relevant test cases from https://github.com/hughsk/flat/blob/master/test/test.js

I decided to not support nested maps for now:

{a.b: 123, a: {c: 321}}

There is one failing test for a map inside a list:

test.0.a: 123

Are you available to take a look?

[Pana-g]

Hi @danilofuchs ! Thanks for the feedback! Indeed there were some issues with the unflatten function, I also found some issues in some of the tests and fixed them as well!

[danilofuchs]

Great!
I added a check to disallow nested maps at all. I'll generate a release

[danilofuchs]

Released!