Added CONFIG_FILE, test for file-read/write permissions.
Added CONFIG_FILE, test for file-read/write permissions.

Credentials are separated from config items.

ee-in/python-api,plotly/plotly.py,ee-in/python-api,plotly/plotly.py,ee-in/python-api,plotly/python-api,plotly/python-api,plotly/plotly.py,plotly/python-api