Error reporting accessing client.project instead of client._project.

[daspecster]

Originally from @DizzeePascall.

When running the examples from the documentation, I get the following error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/laurence/miniconda3/envs/sonalytic/lib/python3.5/site-packages/google/cloud/error_reporting/client.py", line 320, in report
    report_location=report_location)
  File "/home/laurence/miniconda3/envs/sonalytic/lib/python3.5/site-packages/google/cloud/error_reporting/client.py", line 277, in _send_error_report
    self.report_errors_api.report_error_event(error_report)
  File "/home/laurence/miniconda3/envs/sonalytic/lib/python3.5/site-packages/google/cloud/error_reporting/client.py", line 162, in report_errors_api
    self._report_errors_api = make_report_error_api(self)
  File "/home/laurence/miniconda3/envs/sonalytic/lib/python3.5/site-packages/google/cloud/error_reporting/_gax.py", line 44, in make_report_error_api
    return _ErrorReportingGaxApi(gax_client, client.project)
AttributeError: 'Client' object has no attribute 'project'

Disabling GRPC via the GOOGLE_CLOUD_DISABLE_GRPC environment variable fixes this.

I'm running on an Ubuntu 14.04 compute instance with python 3.5.3 and version 023.1 of the google-cloud-error-reporting project