BUG: Issue in the gbq module when authenticating on remote servers #8489
Resolve issue where gbq authentication on remote servers fails silently.

Travis is green
 @parthea can you update, I think should just raise an informative message
 @jreback 

I'm still working on this PR. I removed my last commit, which automatically closed the pull request. It should open when I submit a new commit.

I want to provide users with a simple way to create the required `bigquery_credentials.dat` file. Can I add a new function `gbq.authorize()` to do this?

Then I can raise an informative error message if the credentials are missing or invalid which tells the user to first call the `gbq.authorize()` function. When users call the `gbq.authorize()` function, the following message will appear: `'Please visit the following url to obtain an authorization code:'` Users then will visit the web page to get the authorization code, and then paste it in.
 @parthea `.authorize` sounds reasonable
 Add  `gbq.authorize()` method
 All tests passed in my local environment. Waiting on travis. 

```
nosetests test_gbq.py -v
test_should_be_able_to_get_a_bigquery_service (pandas.io.tests.test_gbq.TestGBQConnectorIntegration) ... ok
test_should_be_able_to_get_results_from_query (pandas.io.tests.test_gbq.TestGBQConnectorIntegration) ... ok
test_should_be_able_to_get_schema_from_query (pandas.io.tests.test_gbq.TestGBQConnectorIntegration) ... ok
test_should_be_able_to_get_valid_credentials (pandas.io.tests.test_gbq.TestGBQConnectorIntegration) ... ok
test_should_be_able_to_make_a_connector (pandas.io.tests.test_gbq.TestGBQConnectorIntegration) ... ok
test_bad_project_id (pandas.io.tests.test_gbq.TestReadGBQIntegration) ... ok
test_bad_table_name (pandas.io.tests.test_gbq.TestReadGBQIntegration) ... ok
test_column_order (pandas.io.tests.test_gbq.TestReadGBQIntegration) ... ok
test_column_order_plus_index (pandas.io.tests.test_gbq.TestReadGBQIntegration) ... ok
test_download_dataset_larger_than_200k_rows (pandas.io.tests.test_gbq.TestReadGBQIntegration) ... ok
test_index_column (pandas.io.tests.test_gbq.TestReadGBQIntegration) ... ok
test_malformed_query (pandas.io.tests.test_gbq.TestReadGBQIntegration) ... ok
test_should_properly_handle_arbitrary_timestamp (pandas.io.tests.test_gbq.TestReadGBQIntegration) ... ok
test_should_properly_handle_empty_strings (pandas.io.tests.test_gbq.TestReadGBQIntegration) ... ok
test_should_properly_handle_false_boolean (pandas.io.tests.test_gbq.TestReadGBQIntegration) ... ok
test_should_properly_handle_null_boolean (pandas.io.tests.test_gbq.TestReadGBQIntegration) ... ok
test_should_properly_handle_null_floats (pandas.io.tests.test_gbq.TestReadGBQIntegration) ... ok
test_should_properly_handle_null_integers (pandas.io.tests.test_gbq.TestReadGBQIntegration) ... ok
test_should_properly_handle_null_strings (pandas.io.tests.test_gbq.TestReadGBQIntegration) ... ok
test_should_properly_handle_null_timestamp (pandas.io.tests.test_gbq.TestReadGBQIntegration) ... ok
test_should_properly_handle_timestamp_unix_epoch (pandas.io.tests.test_gbq.TestReadGBQIntegration) ... ok
test_should_properly_handle_true_boolean (pandas.io.tests.test_gbq.TestReadGBQIntegration) ... ok
test_should_properly_handle_valid_floats (pandas.io.tests.test_gbq.TestReadGBQIntegration) ... ok
test_should_properly_handle_valid_integers (pandas.io.tests.test_gbq.TestReadGBQIntegration) ... ok
test_should_properly_handle_valid_strings (pandas.io.tests.test_gbq.TestReadGBQIntegration) ... ok
test_unicode_string_conversion_and_normalization (pandas.io.tests.test_gbq.TestReadGBQIntegration) ... ok
test_zero_rows (pandas.io.tests.test_gbq.TestReadGBQIntegration) ... ok
test_read_gbq_with_no_project_id_given_should_fail (pandas.io.tests.test_gbq.TestReadGBQUnitTests) ... ok
test_should_return_bigquery_booleans_as_python_booleans (pandas.io.tests.test_gbq.TestReadGBQUnitTests) ... ok
test_should_return_bigquery_floats_as_python_floats (pandas.io.tests.test_gbq.TestReadGBQUnitTests) ... ok
test_should_return_bigquery_integers_as_python_floats (pandas.io.tests.test_gbq.TestReadGBQUnitTests) ... ok
test_should_return_bigquery_strings_as_python_strings (pandas.io.tests.test_gbq.TestReadGBQUnitTests) ... ok
test_should_return_bigquery_timestamps_as_numpy_datetime (pandas.io.tests.test_gbq.TestReadGBQUnitTests) ... ok
test_that_parse_data_works_properly (pandas.io.tests.test_gbq.TestReadGBQUnitTests) ... ok
test_to_gbq_should_fail_if_invalid_table_name_passed (pandas.io.tests.test_gbq.TestReadGBQUnitTests) ... ok
test_to_gbq_with_no_project_id_given_should_fail (pandas.io.tests.test_gbq.TestReadGBQUnitTests) ... ok
test_create_dataset (pandas.io.tests.test_gbq.TestToGBQIntegration) ... ok
test_create_table (pandas.io.tests.test_gbq.TestToGBQIntegration) ... ok
test_dataset_does_not_exist (pandas.io.tests.test_gbq.TestToGBQIntegration) ... ok
test_dataset_exists (pandas.io.tests.test_gbq.TestToGBQIntegration) ... ok
test_delete_dataset (pandas.io.tests.test_gbq.TestToGBQIntegration) ... ok
test_delete_table (pandas.io.tests.test_gbq.TestToGBQIntegration) ... ok
test_generate_schema (pandas.io.tests.test_gbq.TestToGBQIntegration) ... ok
test_google_upload_errors_should_raise_exception (pandas.io.tests.test_gbq.TestToGBQIntegration) ... ok
test_list_dataset (pandas.io.tests.test_gbq.TestToGBQIntegration) ... ok
test_list_table (pandas.io.tests.test_gbq.TestToGBQIntegration) ... ok
test_list_table_zero_results (pandas.io.tests.test_gbq.TestToGBQIntegration) ... ok
test_table_does_not_exist (pandas.io.tests.test_gbq.TestToGBQIntegration) ... ok
test_upload_data (pandas.io.tests.test_gbq.TestToGBQIntegration) ... ok
test_upload_data_if_table_exists_append (pandas.io.tests.test_gbq.TestToGBQIntegration) ... ok
test_upload_data_if_table_exists_fail (pandas.io.tests.test_gbq.TestToGBQIntegration) ... ok
test_upload_data_if_table_exists_replace (pandas.io.tests.test_gbq.TestToGBQIntegration) ... ok
pandas.io.tests.test_gbq.test_generate_bq_schema_deprecated ... ok

----------------------------------------------------------------------
Ran 53 tests in 357.736s

OK
```
 Ready for review. Travis is green.
