text: Title: Speed up test by using shared global variable
  Body: Use pytest fixture global variable to share dataframes to prevent having to load in the test dataset every time across the different tests. For example: 
  ![image](https://user-images.githubusercontent.com/5554675/99403865-e9532080-2925-11eb-8df3-c8f67758e01f.png)
  
  This might also help resolve #97 .