Fix typo in Association Category.
Fix typo in Association Category.

Fixes #30.

HackPartners/bigdatadarwin,HackTrain/bigdatadarwin,HackTrain/bigdatadarwin,grundleborg/darwinpush,fasteroute/darwinpush,HackTrain/darwinpush,HackTrain/bigdatadarwin,HackPartners/bigdatadarwin,HackPartners/bigdatadarwin,HackPartners/darwinpush