Move files to directories.

I am setting up the repository to be able to install it.
Change name to avoid confusion.

I preferred to change the name of the python file to no confuse with the
directory.
Move docstring from main.py to __ini__
Load chemical elements dictionary from HOME

When installing the package, it will copy the `chemical_elements.json`
file to a hidden folder in the `home `directory`. The script now read it
from there.
Import function in order to use on script.

I explicitly imported the `find` function so it can be also imported in
the script.
Minor fix.

* Remove unecessary import.
* Make it look for the `fort.19` in the right path.
Fix calling function.

Since I have changed how to call the main function, I have also to
change it here.
Add MIT license
Ignore build folder
Create a installation setup