text: Title: Add Finance Notebook to Provide Examples of convert_currency() and inflate_currency()
  Body: # Brief Description
  
  I'd like to write a notebook that provides a very brief example of how to use the finance submodule's convert_currency() and inflate_currency() methods.  The notebook would read in a single data frame (or create a simple example data frame in place), and then call on the two aforementioned methods to provide examples of their use.
  
  This notebook would likely cover the following pyjanitor functions:
  
  - finance.convert_currency()
  - finance.inflate_currency() 
  
  # Dataset
  
  This notebook would be focused on showing the functionality and results of the convert_currency() and inflate_currency() methods; therefore, it may just be easiest to create a very simple/minimal dataframe with random numeric values that we assume represent a given currency (e.g., USD) and dollar year.
  