Always use print as a function

Using it as a statement is bad form
Improve discusion about sets

Specify that the actual type itself may not be that
important, but that types have different abilities and
that is awesome.
Homogenized capitalization and fonts throughout
Merge pull request #65 from njvack/print-function

Print function
Merge pull request #66 from njvack/improve-sets

Improve discusion about set
reformatted areacode exercise
Merge pull request #67 from dmnielsen/2014-08-04-Davidson

Homogenized capitalization and code font throughout