Solving little errors while reading the book

[AlexanderKunkel]

This is a fix of little errors and warnings i had with Python 3.6.2 and NumPy 1.13.1

[pep8speaks]

Hello @AlexanderKunkel! Thanks for submitting the PR.

• In the file code/optional-py-scripts/ch03.py, following are the PEP8 issues :

Line 111:1: E305 expected 2 blank lines after class or function definition, found 1 Line 133:1: E305 expected 2 blank lines after class or function definition, found 1 Line 164:1: E305 expected 2 blank lines after class or function definition, found 1 Line 334:1: E305 expected 2 blank lines after class or function definition, found 1

• In the file code/optional-py-scripts/ch05.py, following are the PEP8 issues :

Line 178:1: E305 expected 2 blank lines after class or function definition, found 1 Line 600:1: E305 expected 2 blank lines after class or function definition, found 1

[rasbt]

Thanks a lot! While I've updated all the Jupyter Notebooks, I totally forgot about the scripts versions!