text: Title: [DOC] Update pandas example in the README?
  Body: # Brief Description of Fix
  
  Right now, the pandas example in the README shows what I (IMHO) would say is "bad" pandas code. I would rather write it as something like
  
  ```python
  In [15]: df = (
      ...:    pd.DataFrame(company_sales)
      ...:     .drop(columns="Company1")
      ...:     .dropna(subset=['Company2', 'Company3'])
      ...:     .rename(columns={"Company2": "Amazon", "Company3": "Facebook"})
      ...:     .assign(Google=[450.0, 550.0, 800.0])
      ...: )
      ...: df
  Out[15]:
    SalesMonth  Amazon  Facebook  Google
  0        Jan   180.0     400.0   450.0
  1        Feb   250.0     500.0   550.0
  3      April   500.0     675.0   800.0
  ```
  
  Thoughts on updating that example? I would certainly keep the current one, since it makes it clear that pandas *allows* the "bad" style, while pyjanitor doesn't. But I think it'd be nice to include the "good" style as well :)