Decrease line lengths by one

Although people speak of 80, 79 is actually the number they mean, because terminals will tend to need an extra, blank line if you write 80-character-wide lines.

These changes are in line with PEP 8’s recommendations:

> Limit all lines to a maximum of 79 characters.

> …

> Some teams strongly prefer a longer line length. For code maintained exclusively or primarily by a team that can reach agreement on this issue, it is okay to increase the nominal line length from 80 to 100 characters (effectively increasing the maximum length to 99 characters), provided that comments and docstrings are still wrapped at 72 characters.