inconsistent link to COS directory for model files

[vabarbosa]

the README contains this link to the model files:

• http://max-assets.s3-api.us-geo.objectstorage.softlayer.net/object_detection/ssd_mobilenet_v1_coco_2017_11_17.tar.gz

this works. however, it is different than the link in the Dockerfile:

• http://max-assets.s3-api.us-geo.objectstorage.softlayer.net/object-detector/1.0/model.tar.gz

i would expect both of these to point to the same set of model files.
in addition, both of the links should be pointing to the new US cross region:

s3.us.cloud-object-storage.appdomain.cloud

because the old one has been deprecated:

s3-api.us-geo.objectstorage.softlayer.net