separate Yoneda and Coyoneda
add Coyoneda instances
CoyonedaTest
Detailed example of Writer usage.
removed comments from Scala worksheet.
removed string interpolation
removed usage of foreach/ Each
Add Resources section to README

Hopefully this is helpful to newcomers.

In particular, it is very difficult to find the Scaladocs via web search. I don't know if I ever would have found them if it weren't for the topic in #scalaz on IRC.
Merge pull request #656 (up until e6fc611)

Improved example of Writer usage.
Merge pull request #652 from xuwei-k/coyoneda-instances

Coyoneda instances
Merge pull request #664 from ceedubs/patch-1

Add Resources section to README