Removes usage of numpy deprecated types (int and float)

[pedrolimasi]

Fixes dependency issue where latest numpy would not work with pyfrac, and installing an older version of it would unleash dependency hell on my computer. Deprecated numpy types are np.int and np.float

[Skonki]

Where are we with these adaptions? If they are resolved we could merge.

[pedrolimasi]

This is a single commit fix. I did not plan anything else and, from my quick search, this is the only change in numpy that had any effect in pyfrac.

Feel free to merge.

[carloperuzzo]

Thanks. Merge completed.