text: Title: [ENH] Unit Conversion
  Body: # Brief Description
  
  I would like to propose a set of `engineering` methods that would convert units (e.g., Fahrenheit to Celsius, or Pascals to mmHg, etc.) as well as prefixes (e.g., milligrams to kilograms, kWh to MWh, etc.).
  
  This could go down a big rabbit hole.  But maybe we could rely on [Pint](https://pint.readthedocs.io/en/0.9/), or a similar package.
  
  # Example API
  
  ```python
  # Convert a column of temperatures in Celsius to Fahrenheit
  df.convert_units(column_name='temperature_c',
                   existing_units='C',
                   to_units='F',
                   create_new_column=False)
  ```
  