Update unit tests to read Bing Maps API key from an environment variable
Update unit tests to read Bing Maps API key from an environment variable

To allow the Bing tests to run in CI builds without hardcoding an API key.

lliss/python-omgeo,azavea/python-omgeo,azavea/python-omgeo,WikiRealtyInc/python-omgeo,lliss/python-omgeo,WikiRealtyInc/python-omgeo