Change links to github repos where appropriate #66

Didn't update links for these testing frameworks because they are more software than libraries, and have a few different packages involved:
http://onsi.github.io/ginkgo/
http://labix.org/gocheck

Mgo isnt hosted on github, changed it to the godoc documentation page at:
http://godoc.org/labix.org/v2/mgo

Didn't change the go_generate doc:
https://docs.google.com/document/d/1V03LUfjSADDooDMhe-_K59EgpTEm3V8uvQRuNMAEnjg/edit