Fix setup.py for systems without numpy
Fix setup.py for systems without numpy

Systems without numpy installed globally couldn't build cython that uses numpy
menpo/menpo,grigorisg9gr/menpo,jabooth/menpo-archive,mozata/menpo,yuxiang-zhou/menpo,jabooth/menpo-archive,mozata/menpo,jabooth/menpo-archive,mozata/menpo,menpo/menpo,yuxiang-zhou/menpo,patricksnape/menpo,mozata/menpo,patricksnape/menpo,grigorisg9gr/menpo,grigorisg9gr/menpo,yuxiang-zhou/menpo,jabooth/menpo-archive,patricksnape/menpo,menpo/menpo