ENG-9909 add support for path-based multi-tenancy

[dfreidin]

Add new support for path-based multi-tenancy, with options in client initialization.

• new base_path parameter to explicitly set the base path for the environment
• ability to extract the base path if a full base url is given at initialization
  • base_path parameter will take precedence
• should be backwards compatible if no path is given

Manual testing can be done against https://sm-nested-path.test.sightmachine.io/nested/one/two/:

from smsdk import client

cli = client.Client('sm-nested-path.test', base_path='/nested/one/two/')

# OR:
# cli = client.Client('sm-nested-path.test.sightmachine.io/nested/one/two/')

cli.login('apikey', key_id='<your_api_key>', secret_id='<your_api_secret'>')

cli.get_machine_type_names()
# ['Packer', 'Palletizer', 'L1 Warmer', 'Electricity', 'Line 1', 'Filtec', 'Wrapper', 'L1-Depal', 'Empty Can Conveyor', 'L1 Case Conveyor', 'Filler', 'L1 Full Can Conveyor', 'Blender_1']

Note: The 14 circleci test failures all exist in master as well, not sure why. Perhaps some data has changed in the demo environment or something like that.