Fixed broken links in README
Fixed broken links in README

Replaced Mike's twitter link with his new handle.
Replace direct GitHub link to Scalaz's Monoid.java with doc from TypeLevel.
lucaslanger/algebird,twitter/algebird,sid-kap/algebird,erikerlandson/algebird,nevillelyh/algebird,sid-kap/algebird,nvoron23/algebird,nkhuyu/algebird,nvoron23/algebird,sid-kap/algebird,nevillelyh/algebird,nvoron23/algebird,vidma/algebird,nevillelyh/algebird,nkhuyu/algebird,twitter/algebird,erikerlandson/algebird,lucaslanger/algebird,nkhuyu/algebird,lucaslanger/algebird,erikerlandson/algebird,vidma/algebird,vidma/algebird