Merge pull request #10 from afronski/master

Fixing typos and Removing empty lines
Fixes typo (weekly => weakly)
Merge pull request #11 from ZeissS/patch-1

Fixes typo (weekly => weakly)
Start section on PropER
More on dialyzer
Merge
starting on tagged types
add best practices chapter
more on eunit
move some text to the best practices chapter
a bit of tweeking
Organize Chapters
new chapter about wrangler
finish chapter reorganization
start working on how erlang defines types
start on algebraic data types
starting on refactoring
Fixing typos in chapter 4
Merge pull request #13 from jwarwick/04_typos

Fixing typos in chapter 4
Fixing typos in chapter 05