Add support for user specified regions

[tkasu]

Currently, job sent to AI Platform is always as specified in function get_region():

cloud/src/python/tensorflow_cloud/core/gcp.py

Line 73 in 8644935

def get_region():

It would be useful if the user could specify the region, e.g. as a parameter in tfc.run.

[SinaChavoshi]

Hi Tomi,

Thank you so much for raising this! this is definitely high on our radar. At the same time if you or anybody else is interested to pick this this please let us know.