Update address definition

Addresses are the 160-bit hash of a public key, multisignature addresses begin with three (3).
Add missing comma
Add more missing commas
Merge branch 'develop' of https://github.com/jbisterfeldt/bitcoinbook into jbisterfeldt-develop
Minor copyediting following merge from issue #109
Merge branch 'jbisterfeldt-develop' into develop
Merge pull request #110 from kargakis/ch08-fixes

Add missing comma
Merge pull request #111 from kargakis/ch09-fixes

Add more missing commas
Reverting changes from Issue #109 back to its original