MAINT bump up required numpy version to 1.6.1
MAINT bump up required numpy version to 1.6.1

This is the numpy version in Ubuntu 12.04 LTS and is consistent
with the scikit-learn requirement

aabadie/joblib,aabadie/joblib,karandesai-96/joblib,karandesai-96/joblib,joblib/joblib,tomMoral/joblib,joblib/joblib,lesteve/joblib,lesteve/joblib,tomMoral/joblib