Dropping usage of "size" to measure (resumable) bytes uploaded.

[dhermes]

Also made some tweaks in nox.py to allow passing through positional args, e.g.

nox -s "unit_tests(python_version='3.6')" -r -- --pdb

/cc @tseaver

This is required (with a release) to finish googleapis/google-cloud-python#3555. As I stated there, I made a bad assumption that size would always be in the 200 response when a resumable upload is concluded.

---

For "inspection", compare a Storage response

{
  "bucket": "{BUCKET}",
  "contentType": "text/plain",
  "crc32c": "MR/5OA==",
  "etag": "CMm6nMn0mNUCEAE=",
  "generation": "1500589786078537",
  "id": "{BUCKET}/{FILENAME}.txt/1500589786078537",
  "kind": "storage#object",
  "md5Hash": "vl1dN1Qtdfk6hwlEWfdmeA==",
  "mediaLink": "https://www.googleapis.com/download/storage/v1/b/{BUCKET}/o/{FILENAME}.txt?generation=1500589786078537&alt=media",
  "metageneration": "1",
  "name": "{FILENAME}.txt",
  "selfLink": "https://www.googleapis.com/storage/v1/b/{BUCKET}/o/{FILENAME}.txt",
  "size": "3",
  "storageClass": "STANDARD",
  "timeCreated": "2017-07-20T22:29:46.047Z",
  "timeStorageClassUpdated": "2017-07-20T22:29:46.047Z",
  "updated": "2017-07-20T22:29:46.047Z"
}

to a BigQuery response

{
  "configuration": {
    "load": {
      "createDisposition": "CREATE_NEVER",
      "destinationTable": {
        "datasetId": "dml_tests_1500588804031",
        "projectId": "{PROJECT}",
        "tableId": "test_table"
      },
      "schema": {
        "fields": [
          {
            "mode": "NULLABLE",
            "name": "greeting",
            "type": "STRING"
          }
        ]
      },
      "skipLeadingRows": 1,
      "sourceFormat": "CSV",
      "writeDisposition": "WRITE_EMPTY"
    }
  },
  "etag": "\"ermsQgwazUAYa5aKJk06ue7LJtk/6j_Fsvq--9PWiausL_U0gZdiOaQ\"",
  "id": "{PROJECT}:job_CNzVVbYe_lc5oY0J-h_WX-Oc0lQ",
  "jobReference": {
    "jobId": "job_CNzVVbYe_lc5oY0J-h_WX-Oc0lQ",
    "projectId": "{PROJECT}"
  },
  "kind": "bigquery#job",
  "selfLink": "https://www.googleapis.com/bigquery/v2/projects/{PROJECT}/jobs/job_CNzVVbYe_lc5oY0J-h_WX-Oc0lQ",
  "statistics": {
    "creationTime": "1500588807360",
    "startTime": "1500588807880"
  },
  "status": {
    "state": "RUNNING"
  },
  "user_email": "{USERNAME}@developer.gserviceaccount.com"
}