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
Another missing comma
Updating GitHub contributors
Merge pull request #113 from physicsdude/develop

fix superscript
Merge pull request #115 from kargakis/ch02-fix

Add another missing comma
Update preface.asciidoc

bitcoin address clearer explanation
Update preface.asciidoc

I think it's better to explain the value and usage of a fee, instead of a more technical definition that identifies how it works.
It is possible for a transaction to be processed without a fee.
Update preface.asciidoc

Maintain consistency.  If you're gonna show an example bitcoin address, should show an example private key.  It also helps to understand it further when you can see an example.
Update preface.asciidoc

A clearer explanation of the value a wallet brings to a user
Update ch01.asciidoc

As I read through the history of Bitcoin section I kept asking when are you going to get to the part about Bitcoin.  I think half of that section is really events leading up to Bitcoin, as well Bitcoin didn't have any history until it was invented.
Update ch01.asciidoc

accidentally put What is Bitcoin, for History of Bitcoin
Update ch01.asciidoc

Identifying the potential pains that Bitcoin can solve, quantifying how big of an impact the innovation can really have.  This should hopefully get the reader excited about the possible power their code can have, and encourage them even more to learn more about Bitcoin.