Add bigquery scope for google credentials
Bigquery requires scoped credentials when loading application default credentials

Quick test code below, it will return "invalid token" error. When uncomment the create_scoped() statement, the code run correctly without any error.
```bash
# use google default application credentials
export GOOGLE_APPLICATION_CREDENTIALS=/PATH/TO/GOOGLE_DEFAULT_CREDENTIALS.json
```
```python
import httplib2

from googleapiclient.discovery import build
from oauth2client.client import GoogleCredentials

credentials = GoogleCredentials.get_application_default()
#credentials = credentials.create_scoped('https://www.googleapis.com/auth/bigquery')

http = httplib2.Http()
http = credentials.authorize(http)

service = build('bigquery', 'v2', http=http)

jobs = service.jobs()
job_data = {'configuration': {'query': {'query': 'SELECT 1'}}}

jobs.insert(projectId='ubcxdata', body=job_data).execute()
```

Another PR is made to pandas-gbq repo for master branch: https://github.com/pydata/pandas-gbq/pull/33

 - [x] tests added / passed
 - [x] passes ``git diff upstream/master --name-only -- '*.py' | flake8 --diff``
