Remove some np.int and np.float because of numpy 0.20.0

[samuelgarcia]

#979

See https://numpy.org/devdocs/release/1.20.0-notes.html#using-the-aliases-of-builtin-types-like-np-int-is-deprecated

[pep8speaks]

Hello @samuelgarcia! Thanks for opening this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file neo/io/tiffio.py:

Line 112:100: E501 line too long (105 > 99 characters)