Chapter 2: Some hardware is redundant

[akorb]

In chapter 2 about controlling the LED with a button.
The python and C code put the buttonPin into pull up mode which leads to the usage of the internal resistors of the RasberryPi.
Therefore, some of the shown components in the diagram are not required (tested by myself and works):

The GPIO18 port can be connected directly to GND with only the button in between.

See https://github.com/raspberrypilearning/physical-computing-guide/blob/master/pull_up_down.md for more information