Ch 15 Better Alt Text (#252)

* better alt text ch15.0

* better alt text ch15.1

* better alt text ch15.0 take 2

* better alt text ch15.2

* better alt text ch15.23

* better alt text ch15.4

* better alt text ch15.4 take 2

* better alt text ch15.5

* better alt text ch15.6

* remove extra cells 15.1

Author: pancakereport