Add Statement of Need

[engnadeau]

Please add a Statement of Need to your README/documentation. It's preferable that this is one of the first things a reader would see in the README.

cc openjournals/joss-reviews#2120

[raphaeltimbo]

Hi there @nnadeau ! Thank you for your comments.
We have just released v0.3.0 and I have updated de README file to give a better explanation on the use of our software. Let us know if that is ok to you.

[engnadeau]

👍