text: Title: Improve warning message format
  Body: The current warning messages via `warnings.warn` is hard to read due to the call trace that is printed alongside the warning. This is true even when we set the `stacklevel` parameter in `warnings.warn`. For example:
  ![image](https://user-images.githubusercontent.com/5554675/99404699-e60c6480-2926-11eb-8201-acbb6b7755ad.png)
  We should add warnings formatted that display nicer warning messages following best practices for warning formatting (refer to warning messages formatting in numpy and pandas?). This could possibly be achieved by a global levels setting or a warnings formatter.
  
  
  