text: Title: A "no formatting" mode for CI runs which don't support text formatting
  Body: **Is your feature request related to a problem? Please describe.**
  
  Snapshot failures in my Jenkins runs show the colour codes which make it hard to read the diffs.
  
  ![image](https://user-images.githubusercontent.com/1297096/81453860-a2a39300-9158-11ea-9888-dfc066d5c070.png)
  
  **Describe the solution you'd like**
  
  An opt-in `--no-formatting` (`--no-colors`) mode.
  
  **Describe alternatives you've considered**
  
  Using a better CI runner.
  
  **Additional context**
  
  jest has a `--no-colors` mode.