In many places a `pass` instruction is used in loops to wait until we hear back
back from the display. This causes the loop to execute continuously which uses
all of the available CPU, if we instead sleep for 1ms, we don't lose much time
(less than 1ms each wait) and we dramatically reduce the load on the CPU.
Before the change (updating a 3-color 2.13" display):
```
time python3 ./update_display
real 0m19.664s
user 0m17.622s
sys 0m1.046s
```
After the change:
time python3 ./update_display
real 0m19.730s
user 0m3.563s
sys 0m0.792s1
The total time to run the script is about the same, but the CPU time has reduced dramatically.
