added cython

while executing "make" command in "COCO API installation" in linux ubuntu got  "gcc: error: pycocotools/_mask.c: No such file or directory
"
this thread : cocodataset/cocoapi#141
solved the issue ie: after installing cython

added cython

while executing "make" command in "COCO API installation" in linux ubuntu got  "gcc: error: pycocotools/_mask.c: No such file or directory
"
this thread : cocodataset/cocoapi#141
solved the issue ie: after installing cython

Minor fixes and updates