Clean up minimal example of README

[baniasbaabe]

You can clean up the example from the README from:

import opendatasets as od
dataset_url = 'https://www.kaggle.com/tunguz/us-elections-dataset'
od.download('https://www.kaggle.com/tunguz/us-elections-dataset')

to:

import opendatasets as od
od.download('https://www.kaggle.com/tunguz/us-elections-dataset')

or:

import opendatasets as od
dataset_url = 'https://www.kaggle.com/tunguz/us-elections-dataset'
od.download(dataset_url)